computer science Archives - NeuralLantern.com

Representing a Directed Unweighted Graph with an Adjacency Matrix

mike — Mon, 09 Nov 2026 06:56:48 +0000

Learn how to represent a directed unweighted graph using an adjacency matrix. We cover why a two dimensional matrix is really just a one dimensional array under the hood, making cell access and updates extremely fast. For directed graphs the starting node is the row and the ending node is the column. A zero means no connection and a one means an edge exists. Self connections are not implied by default. Adding or removing an edge is constant time. Directed graphs do not produce a symmetric matrix like undirected ones. This is one practical way your program can store and work with a graph. If you have been following the previous videos on undirected graphs this builds directly on that. The next video will cover directed weighted graphs with an adjacency matrix. Thanks for watching and I hope you picked up something useful.

00:00 Intro to Directed Unweighted Graphs
00:01 Matrix Stored as Contiguous 1D Array
03:09 Building the Adjacency Matrix
04:25 Filling Outgoing Edges Node by Node
09:43 Directed Graphs Are Not Symmetric
10:36 Adding a New Edge
11:08 Adding Self-Connections
11:53 Removing an Edge
13:04 Adding Bidirectional Edges
15:28 Next Video and Outro

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hello there. Let’s talk about representing a directed, unweighted graph inside your

machine using an adjacency matrix. It’s going to be fun.

Okay, sorry about that. Anyway, so I hope you’ve been watching my previous videos.

We covered already how to do an undirected weighted graph and also unweighted graph

using an adjacent

and also unweighted graph using an adjacency matrix we’re going to basically represent a graph

inside of the machine like this is one of the ways that your machine can do it we’re not going to

talk about code exactly but you know kind of allude to code but this is this is a really good

way to you know get started in practicing the concept okay first thing i want to say i’ve said

this in my previous videos i’m sorry if you’ve been watching all of them is that this matrix

this two-dimensional matrix it’s really just a one-dimensional array think about this we have

Thank you for watching.

array think about this we have some numbers in an array I’m going to put six numbers in there

we could just as easily represent this as a two-dimensional matrix a two-dimensional array

right it’s the same amount of numbers what’s really happening under the hood when you have

a two-dimensional array is your computer just has it as a one-dimensional array so the question is

why is that useful oh hang on okay anyway so what i wanted to say is that you see

So what I wanted to say is that you see a two-dimensional matrix,

but really what’s happening inside your computer is a one-dimensional matrix.

I’m just going to make a one-dimensional matrix.

I’m going to say we’re putting numbers in the matrix.

I’m just going to put like, you know, six hashes or pound signs or hashtags in the modern era.

So a one-dimensional array could be represented as a two-dimensional matrix

if we just reformat it a little bit.

last part of that first array on a second line that’s what’s happening in the computer

even if you’re working with a two-dimensional array in your computer it’s still just a

one-dimensional array under the hood which means it’s incredibly fast to access one particular

index not necessarily to scooch things remove things and add things but if i wanted to go to

index three and a one-dimensional array if you know time complexities already that’s really fast

That’s constant time. We’ll do time complexities in another video, but um if

but um if i wanted to access you know a certain row in a certain column intuitively you think

well i gotta like scan down and scan to the right uh so maybe it’s slower but it’s not because it’s

still just going to be math to find exactly the right offset in uh your two-dimensional matrix

because it’s really a one-dimensional array all of the items in this array i didn’t say this in

previous videos all the items in this array are contiguously allocated so all we really have to

do is compute an offset from some

compute an offset from some starting memory location so it’s incredibly fast

to read a cell in this matrix and to modify a cell in this matrix you’ll see in a second

that’s well you’ll see in several minutes why that’s one useful feature of a of an adjacency

matrix okay so adjacency matrix uh suppose you’re presented with this matrix you see

i’m sorry with this diagram you see right here this is a graph it’s got direction on all the

edges i really hope i didn’t forget any particular edge i think i’ve got arrows on all of them

think i’ve got arrows on all of them we’ve got nodes and edges and i just

need to figure out how can i put that into a matrix so my computer

my program understands the graph and it it has a representation of the graph

so with directed graphs the start row uh sorry the start node and the end node

actually matter a lot in my other videos where we talked about

undirected graphs we could just easily swap the row and the column

in this matrix and it didn’t really make a difference because the whole matrix

was going to end up being a mirror anyway.

was going to end up being a mirror anyway but that’s not going to happen this time so what i’m

going to say for the way that i like to do things is the starting node is the row and the ending

node is the column so this is also an unweighted diagram an unweighted graph so we don’t really

need to store floats or infinities or anything like we did in the other video we can just say

that no connection means no connection is a zero and yes connection is a one of course you could

You could still do that with floats if you want to,

of course you could still do that with floats if you want to but whatever you could have a a matrix

of booleans if you really wanted to like true and false and true and false but you know for this

diagram we’re going to say 0 and 1. so i’m going to start with node number one and node number one

therefore is going to be the the source node and i’m going to see where does where does it go out

to what edges are outbound from the number one so the start node is the one that means the row is

one that i’m working with and the destination nodes or the end nodes or the sync nodes those

Those will be the calls.

nodes are the sync nodes those will be the columns so i’m not really going to look at how six is

coming into one because i’m only interested right now in what uh what one starts uh in terms of an

edge you know what edges come out of one so one forget about the six and the two those are incoming

edges i’m just going to look at the outgoing edges so one goes out to three and four and five so

by default in our diagrams at least at this point we’re going to say

our diagrams at least at this point we’re going to say that self connections are not implied

meaning by default if i don’t see an actual edge on the diagram going from one back into one then

i’m going to say one is not connected to itself so i’m gonna put a zero to say there’s no connection

uh one going to uh the two that’s not happening because two is actually going into one

so i’m going to put another zero then uh there uh one going to three that is happening

uh one going to three that is happening so i’m gonna put a one so one does have an outbound

connection or an edge to three so i’m gonna put a one in that row and column

one going to four uh yes so i’m gonna put a one one going to five uh yes so i’m gonna put a one

there one going to six uh no so i’m gonna put a zero there i should have put you know

edges that go back and forth uh to make this more interesting but you can probably imagine

imagine well i’ll add that maybe later in this video so one going to seven uh nope someone put

a zero so that’s the first row we represented all of the outbound edges from one to some other node

and we used a zero to say it doesn’t exist and a one to say it does exist so then we just move on

to the two so if i’m focusing on the two node then i’m on the two row and its outgoing connections

are going to be represented in the columns.

in the columns so does two go to one yes I’m going to put a one there does two go to itself

self-connections are not implied at this point and then uh hang on a second

does two go to three um nope because three goes into two and not the other way around

uh we’ll add those other edges in a second does two go to four nope does two go to five

nope there’s two

nope does two go to six um i don’t see that so i’m going to say nope and then does two go to seven

uh yes i’m going to put a one so now we’re done with the two um this is a directed graph by the

way so like i said about my previous videos we will not see a mirror at least we won’t necessarily

see a mirror we might accidentally make a mirror depending on what the graph is but we’re not going

to see a mirror. So we have to do this whole graph with no shortcuts. So the

shortcuts so the three uh does it go out to the one that’s a no does it go out to the two

um where the heck is the three oh yeah it goes out to the two

uh no implied self-connections three goes to the four nope three goes to the five yes

3 goes to the 6

nope

3 goes to the 7

uh three goes to the seven nope okay so now we’re done with the three

and then we’ll say now does four go to the one i’m looking at the four where the heck’s the four

i’m losing the four oh four doesn’t go anywhere except for the seven so i can actually just put

like zeros in this whole thing you know just to save a little time oh god there we go but the

four does go to the seventh. I’m going to put a one right there. Okay.

the sevens i’m gonna put a one right there okay so uh the five um it has outbound connections i’m

gonna i’m gonna be cheap here i’m gonna be cheesy the five goes to six and seven so i’m just gonna

put zeros everywhere else so whoops in fact i probably could have just copied that whole row

of zeros and then just overwrote the last two but i guess so the five goes to the six that’s a yes

The 5 goes to the 7. That’s a yes also.

the seven that’s a yes also and then we’re ready for the six the six has three outbound connections

one three and seven so i’m just gonna you know what i’m just gonna copy a whole row i wish i

had a whole row of zeros and i’m gonna maybe change that to a zero real fast and then i’m

gonna say all right where does where does six actually connect to let’s change those zeros to

ones six connects to the uh the one and the three and the seven

and the 7 okay so 1 goes to 1 3 goes to 1 and 7 goes to 1 okay then the 7 uh has no outbound

connections so this is indeed a row of zeros maybe i could have done that one first it would

have been fun oh well uh notice one more time that there’s no mirror so if we like you know

if you trace your eyes along this identity line right here and you were expecting to see a mirror

you would be sadly disappointed.

a mirror you would be sadly disappointed because what would actually happen is not a mirror let me

do the highlighter here and we’ll say we have like an identity line that goes down the middle

and then i’ll just try to highlight some stuff let’s see the three four five six over here on row

uh one and and those columns let’s go now to uh column one and notice how it’s like not the same

three four five six so that’s not

five six so that’s not a mirror because those numbers don’t match so there’s no mirror in

directed graphs in terms of the matrix anyway let’s see i’m going to get rid of these little

pound signs these hashtags uh the next question is uh let’s do a self-connect how do we add an

edge like if i wanted to add an edge from uh you know one to seven for example actually let me

duplicate this first, and then we’ll work on it.

first and then we’ll work on it if i just wanted to add a brand new edge going from one to seven

uh then i just have to make sure that i look at the row one and then look at the seven column

and then just change that value to a one to say did i do that yeah to say that uh the edge now

exists right so that’s pretty easy to add a brand new edge let’s look at self connects now just in

in case um if i wanted to say that four connects to itself i have to do an arrow

4 connects to itself. I have to do an arrow by the way. Did I do an arrow on the last one?

Yeah, okay. 4, we’re saying now it connects to 4. So before we assumed that there were no

self-connections by default. So all the nodes had no self-connections. But the 4, we just added

a self-connection. So that means right here, that 0 is going to change to a 1. Pretty easy and fast

to add an edge. And by the way, how fast was it to just access a cell and modify a value?

modify a value it’s constant time again big O is going to happen in other videos but uh this

is lightning fast for adding and removing edges okay so then the other thing is um let me see

can I do oh I gotta get rid of that how do we remove an edge oh bro bro what’s happening here

just select that oh how do we remove an edge we talked about this in other videos

we talked about this in other videos for our adjacency matrix but it’s pretty easy we just say

all right suppose i just want to kill this edge going from three to two so now there’s

no connection no edge going from three to two um well i just have to go find the appropriate

part of the matrix and that’s it so row three because three was the start node or the source

node row three and then two is the destination node so i’m just gonna like overwrite that with

the zero and now we have effectively removed an edge remember the computer doesn’t actually

See you next time.

Remember, the computer doesn’t actually see this diagram that you’re looking at on the left.

The computer just has the matrix.

The computer doesn’t really even need to know that the 3 is on top visually.

It just needs to know what the 3 is actually connected to.

At least most applications of graphs.

There are some where it’s more visual, and so there needs to be some coordinates.

But just the easiest and most simple way right here with an adjacency matrix doesn’t need that.

Okay, so then the next thing I want to do is…

is um i want to add edges that kind of like point towards you know two nodes that sort of point

towards each other like you know opposing is this going to work yeah opposing uh edges that’s not a

technical term so suppose for the sake of argument that you’re looking at the three and you say well

the three can go outbound to the two but can the two go outbound to the three yeah totally

Okay, so I now have two edges, each going in a different direction between the 3 and the 2.

And by the way, in your mind, you might be thinking,

hey, isn’t that what undirected graphs are doing?

Yeah, basically, you have just an edge that goes in both directions.

Here we have to draw two separate edges.

Then we just have to update the matrix to match.

So I added an edge going from 3 to 2.

So I’m going to go row 3, and then column 2, and…

Oh, sorry, sorry.

originally which worked from three to two that’s why is that what that’s why

there’s a one there but now I just added an edge from two to three so we look at

row two and then column three and then I update that to match so that zero became

a one and it did become a little bit more like a mirror if we went ahead and

added these like you know opposing edges on every single pair of nodes then the

matrix would start to look like a mirror anyways what else can I talk about we’re

We’re at about 16 minutes.

about we’re at about 16 minutes and i’ve lost my mouse cursor what the heck oh there we go i need

i need accessibility controls you know it’s true actually i really need glasses i’ve needed glasses

for a couple of years maybe like five years and for some reason i just can’t get myself to go so

what’s happening now is when people show me memes on their phones my face goes it goes backwards

like this it’s like a it’s like a repellent for my face if you show me a meme i’m like

me a meme i’m like not not fun to live that way so i gotta get glasses should i get a chain i want

a gold chain that’s like studded and like blinged out and then like i have the glasses here only

when i need to read and then it hangs the rest of the time and it maybe it plays music or something

i don’t know i don’t think i’m gonna go that far so uh when we did undirected unweighted i’m just

trying to make sure that i didn’t forget anything there’s no cheesy broccoli in this video directed

and unweighted. Yeah, I guess that was it.

weighted yeah i guess that was it okay so we’re at the end of this particular video i’m going to do

one more before we shift topics the next one is going to be how to represent a directed and

weighted graph inside the machine um using an adjacency matrix okay thank you for watching

this video i hope you learned a little bit of stuff and had a little bit of fun i’ll see you

soon i’m gonna go have a burrito no i’m not i’m just gonna keep recording hey everybody

hey everybody thanks for watching this video again from the bottom of my heart i really

appreciate it i do hope you did learn something and have some fun uh if you could do me a please

a small little favor could you please subscribe and follow uh this channel or these videos or

whatever it is you do on the current social media website that you’re looking at right now

it would really mean the world to me and it’ll help make more videos and grow this community

so we’ll be able to do more videos longer videos better videos or just i’ll be able to keep making

Thank you.

or just i’ll be able to keep making videos in general so please do do me a kindness and uh and

subscribe you know sometimes i’m sleeping in the middle of the night and i just wake up because i

know somebody subscribed or followed it just wakes me up and i get filled with joy that’s exactly

what happens every single time so you could do it as a nice favor to me or you could you could troll

me if you want to just wake me up in the middle of the night just subscribe and then i’ll i’ll

just wake up i promise that’s what will happen also uh if you look at the middle of the screen

right now you should see a

look at the middle of the screen right now you should see a QR code which you can scan in order

to go to the website which I think is also named somewhere at the bottom of this video and it’ll

take you to my main website where you can just kind of like see all the videos I published and

the services and tutorials and things that I offer and all that good stuff and uh if you have a

suggestion for uh uh clarifications or errata or just future videos that you want to see please

leave a comment, or if you just want to say, hey, what’s up? What’s going on?

to say hey what’s up what’s going on you know just send me a comment whatever i also wake up for

those in the middle of the night i get i wake up in a cold sweat and i’m like it would really it

really mean the world to me i would really appreciate it so again thank you so much for

watching this video and um enjoy the cool music as as i fade into the darkness which is coming for us

That’s all.

Thank you.

The post Representing a Directed Unweighted Graph with an Adjacency Matrix appeared first on NeuralLantern.com.

How to Represent an Undirected Unweighted Graph with an Adjacency Matrix

mike — Mon, 12 Oct 2026 06:55:15 +0000

Learn how to store an undirected unweighted graph inside a computer using an adjacency matrix. In this video we build a matrix of ones and zeros where each cell shows whether an edge exists between two nodes. Rows represent the starting node and columns represent the ending node. Because the graph is undirected the matrix ends up as a mirror image across the diagonal. We also cover how to add or remove edges by simply changing a cell value, how self-loops appear on the diagonal, and why this representation lets you check any connection in constant time. The computer only needs the connection data, not the physical layout of the nodes. Perfect if you are learning graph theory, data structures, or preparing for algorithm interviews.

0:00 Introduction to Adjacency Matrix
1:16 Arrays as Two Dimensional Matrices
2:20 Ones and Zeros Represent Edges
3:44 Filling the Matrix for Node One
6:20 Completing the Remaining Nodes
10:38 Finished Matrix and Practice Advice
11:02 Computer Stores Only Connections
11:40 Mirror Property of Undirected Graphs
14:17 Adding and Removing Edges
17:31 Parallel Edges Are Not Supported
18:50 Conclusion and Future Topics

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hey there! Let’s talk about representing an undirected,

unweighted graph in your machine using an adjacency matrix.

All right everybody, so I hope you’ve been watching my previous videos.

I just did some videos on edge list representation. Before that,

I talked about like the basics of graphs and like terminology and stuff like that.

You don’t need

terminology and stuff like that. You don’t need to watch the edge list videos if you’re not

interested in representing using an edge list, but you should probably at least watch the graphing

video basics if you haven’t. Okay, so what are we looking at right here? I’ve just made a graph.

I made a random graph and I kind of like, you know, wired up a bunch of edges to make it kind

of complicated. I then spent a whole bunch of time making this very beautiful two-dimensional

Matrix, just for you. I’m sorry you couldn’t watch me

you i’m sorry you couldn’t watch me write it you know i sometimes i’ll i’ll have people say that

they like when i yell at myself while i’m drawing something sorry it took too long but anyway what

we’re going to do is take these concepts and put them together and we’ll we’ll say this is how we

can represent the graph inside of the machine so what am i even talking about uh well the first

thing is imagine an array in your machine right an array of integers like an array of uh i don’t know

doubles you know an array of whatever so i’m gonna say like 5.4 and like you know 7.7 and

8 and you know like whatever so i’m just like making an array of numbers probably a lot of

you like this notation but inside your machine an array uh that is one-dimensional could be

interpreted as a two-dimensional array so this matrix up here on the top right of the screen

that’s really a one-dimensional ray array inside of the computer it’s just that we choose to treat

it as a two-dimensional array.

a two-dimensional array and um it’s important to understand that you can jump to any cell

in constant time uh just like you can with a one-dimensional array because getting to a certain

cell is really just a simple mathematical formula i think i’m going to do time complexities of this

in a different video so for now i’m just going to say here’s how we represent the diagram first off

let me label this so i don’t forget uh this is definitely where the heck is that how come that’s

That’s not working, okay.

Oh, this is definitely.

okay uh this is definitely an undirected unweighted graph

trying to type with the pen in my hand i have to change my brain okay

so this is an undirected and also unweighted graph

so for the purposes of this particular graph if it’s unweighted that means in the cells um we’re

just we’re not going to put weight because there’s no weight in the graph i mean you could if you

Wanted to.

the graph i mean you could if you wanted to just say that every edge was a weight of one if it was

unweighted but i’m gonna say let’s forget about you know what is the actual value of an edge

because we don’t really have that in this graph and we’ll just say that if an edge exists then uh

we’ll put a we’ll put a one there and if an edge does not exist we’ll put a zero in there

at the corresponding cell we’ll talk about what cells mean you know what edges in a second

The other thing is because it’s undirected, it doesn’t actually matter.

It doesn’t actually matter whether we’re describing a start node or an end node with an edge because it goes in both directions.

So actually what’s going to happen is this graph is going to be a mirror.

I’ll show it to you in a second, but for now we’ll just say it’s not going to matter what the direction is.

I like to do starting nodes as the rows, even though I just said that doesn’t matter.

It’s just the way that I like to do things because it makes it easier to remember how to do this when you start to add direction to the graph.

the graph so one by one i’m going to look at every single node and i’m going to chart what exactly is

going on with that node in the two-dimensional matrix so i’m going to start uh i guess i’m going

to go numerically because that’s kind of easier i’m going to start with the node index 1. so i’m

going to go here at row 1 because i’m going to say that’s my start node and um where does the

one node connect to it connects to node number two so um let’s see actually i think i’m going

I’m going to say that.

actually, I think I’m going to say that it is not self-connected. I mean, if you consider your

graph to have by default every node is connected to itself, you could put a one there across that

little diagonal line that you see. But I’m going to put a zero saying that these nodes are not

connected to themselves, unless we do a little loop from a node to itself. Maybe I should add

that later. So node number one is connected to node number two. I’m going to write a one there

to say that there is a connection.

What do I mean by that?

What do I mean by that? Just to clarify, this, let’s see, the one two edge, that edge that I

just highlighted in pink, that corresponds to this cell. So the start node, I’m going to do

that in maybe orange. The start node is the row number. And maybe I’ll do like, I don’t know,

light blue or something, baby blue for the destination node. And that’s going to be the

column number. So basically just like the row

so basically just like the row number is where the node where you start what node you start at

the column is what node you end at um and then if you see a zero or a one in that particular cell

at that particular row and column it’ll tell you whether there’s an edge there or not

so i’m going to duplicate this real fast so i can erase the markings i just made

and i’m going to say oops whoa whoa what’s happening here i want to get dude

dude are you kidding me can i just erase it like that yeah okay i keep thinking these are lines i

actually made a diagram in a different program so these are not even lines i can’t even erase this

it sucks so um we did the uh the two node so i’m just going to quickly say the one is connected

also to the three yes or no yes that’s a one uh then the one node is connected to the four

uh yes i’m going to put a one the one node is connected to the

the one node is connected to the five yes so i’m going to put a one a lot of connections this is

pretty good uh and then also to the six and not to the seven so if it’s not connected to the seven

i’m going to put a zero there okay we do the same thing for the two node so i’m going to start at

the two node actually let me duplicate this start at the two node and i’m going to say

we’re now looking at the two node oh my gosh

okay I’m gonna put a question mark I guess we’re looking at the two node and

well is the two node connected to the one node yes we just saw that was true

is the two node connected to itself we said in this particular graph there are

no self connections by default because I want to be able to draw them if that

ends up being true is the two connected to the three I see a connection there I

see an edge so I’m gonna put a one is it connected to the four I don’t see an

edge, I’m going to put a zero.

the four i don’t see an edge so i’m gonna put a zero to the five uh yes to the six uh yes and to

the seven um whoops what did i just do uh the two is not connected to the six i was thinking of the

one uh the two connected to the seven yes okay so we just basically do this over and over and

over again until you have a giant matrix of ones and zeros which can very efficiently store um

store um a graph i mean this is pretty much it this is all you have to do i want to do uh let’s

see three is connected to i’m gonna say one one and a two and it’s not connected to itself by

default put a zero it’s connected to the four nope it’s connected to the five

oh gosh i gotta make that even connected to the five

Oh.

i’m losing my brain here uh yes and then uh three connected to the six right three connected to the

seven uh no okay somebody leave me a comment uh if you have a corruption and then for the four

um let’s see dude this is getting out of control for the four um

yes i’m just going to look at the diagram pretty soon we’re going to start realizing something fun

about an underachiever.

realizing something fun about an undirected graph in that it is a mirror in this matrix

so technically you only have to do like one half of the matrix in your code if you wanted to

so i’m gonna say the one exists um one you know what i should have done i should have just filled

this whole thing with zeros and then change the zeros to ones um okay so the four is connected

to the two, yes or no? Nope. All the fours connected to the three? Nope. Fours connect…

Nope, or it’s connected to the 4, we’re going to say no by default, or it’s connected to the 5, nope, it’s only connected to the two things, it’ll just be the 7 I guess, okay, so we’re going to put a nope there, and then a yep for the 7.

Okay, then the 5 is connected to 1, 2, 3, 4, what if I just did a whole bunch of zeros, and then I overwrote only the ones, that would probably be a little bit faster.

bit faster except for this first time i’m doing it okay and then i’ll just copy paste this

tap it past okay i should have done this should i edit that out of the video i don’t know it’s fun

to watch my mistakes so five to one yes five to two no five to three yes uh five to four

we say no by default five to six yes five to seven yes okay i think that was a little bit

faster let’s see how fast it is this time uh the six is connected to the five well let’s say it’s

the one and then uh a one a three a five and a seven right six one three five and seven okay so

going to be one, three, five, seven. That’s probably right. Again, leave me a comment.

probably right again leave me a comment if i screwed something up i did not practice this

i’m just kind of winging it the seven is connected to uh five six two four five six okay so i’m gonna

do two four five six whoops that six didn’t happen let me just do it again okay all right

so now we have it this is a uh an adjacency matrix that represents the graph that you see on the left

Keep in mind that if you saw a matrix, I mean in general you should probably practice doing this both ways, like look at a graph and then you generate the matrix that corresponds to the graph you’re looking at, but also maybe you’re presented with a matrix and you would draw the graph that the matrix represents.

Try to remember that your computer, in almost every program, it doesn’t really know where these nodes are unless it’s a drawing program or something.

if we’re just talking about relationships which is what graphs are kind of good at um then your

computer

um then your computer doesn’t really care that the three is on the top it doesn’t really know that

definitely not with this adjacency matrix representation uh the three in the computer’s

mind could just be anywhere it doesn’t really even think of where the nodes are it’s just

this node is connected to that node and that node is connected to that node and so forth

we just position the nodes somewhere because we’re humans and it’s fun to look at diagrams

but really this is all your computer knows just all these you know little connection numbers here

So, let me duplicate this and I’ll show you something funny about an undirected graph real quick.

Let’s see, how much time? 12? That’s not too bad.

So, if I do, let’s see, I want to do a little highlighter here.

I don’t get a chance to do that very often.

I’m going to do a highlighter across this identity line, you know, the little diagonal.

It’s all zeros for self-connects.

Maybe I’ll change that in a second.

I’ll make one of the nodes connect to itself.

But notice how if I do this.

notice how if i do this in green

notice oh is the highlighter going to be green now keep screwing that up notice how we have

a mirror happening along the identity line so we have like some some ones here right uh so we have

like two three four five six in the one row if we look at the one column we’ll also see two three

four five six it’s a mirror uh pick you know any other numbers you want let’s look at the uh the

The three column.

at the uh the three column the three column has a one there and then it’s got another one and a one

down below at the five and the six so three is hitting two and five and six uh let me look at

the diagram just to make sure i’m doing this right three is hitting uh two and five and six

it should be hitting one also oh right i didn’t highlight that because it was already highlighted

by that other thing okay so then let’s look at the three row and see if we see a mirror also so

two and then the five and the six notice how it’s a mirror you just tilt your head uh and it really

looks like a mirror and sometimes i like to make a joke when i’m explaining this to people uh you

know if you just kind of like tilt your head a little bit it looks like some cheesy broccoli

i’m personally not a fan of cheesy broccoli i mean i love cheese and if you put cheese on my

broccoli i’m gonna be happy but it turns what’s what was healthy food into junk food it’s like

I’m going to be healthy.

I’m going to have broccoli today.

be healthy i’m gonna have broccoli today good for me yay i’ve earned a double bacon cheeseburger

later but then i put cheese all over the broccoli and suddenly it’s junk food again and it’s like i

do get a little fiber and everything but it’s like not really being that healthy anymore so what

should i do i should just get some more healthy food to make up for the junk food broccoli and

then i’m gonna end up putting cheese on the other healthy food and then i just it’s like an endless

cycle and i just keep eating and eating and eating pretty soon there’s no room for a cheeseburger

pretty soon there’s no room for a cheeseburger i don’t know what to tell you anyway um so this

is how you make an undirected unweighted graph uh with an adjacency matrix we’ll talk about time

complexities and other stuff in the future um uh oh i should talk about how to modify edges okay

so first off let me let me create a self loop real fast i’m going to create a self connect

but let’s say that this four is actually connecting to itself uh with like a little

self-loop. Okay. So, oh shoot.

so oh shoot how can i get rid of all those is that going to work yes it’s going to work yes

i should have duplicated this and drawn on the duplicate maybe i actually did that forgot about

it already i don’t even know okay sometimes i have clever ideas and then i forget what i was

doing then the ideas are just not that clever anymore yes okay what about that highlighter

Okay.

i seem to have screwed up the graph somehow

nope okay forget it um we’ll just pretend that it’s fine so i added that four connection

so how do i modify the adjacency matrix well the four uh row starting node with the four column

ending node was a zero indicating no self-connection now that i do have a self-connection

And I’ll just put a one there, four and.

connection i’ll just put a one there four and four and that’s it pretty easy right let me duplicate

this other one so i don’t have to erase that stuff a second time a second time and um what

will we do if we wanted to uh well let me actually sorry everybody let me just do that four one more

time so i think i just erased the wrong thing we’ll say four and four is a one now and so how

can we say that some new edge has been added?

some new edge has been added let’s add an edge between one and seven pretty easy we just go to

the right spot in the adjacency matrix let me add a little orange line here adjacency matrix

to connect number one and number seven that would be uh we could do row one and column seven

so that’s going to be a one and then remember this graph is undirected so it has to be a mirror

so that means uh row seven and column one also has to be a one so it’s still a mirror

so it’s still a mirror that’s pretty much it and remember you can access these cells

in constant time which we’ll talk about more in a future video pretty nice how do you delete

uh an edge let’s pretend that we wanted to delete uh the connection between the five and the three

so i’m going to put maybe like a little squiggly line right here squiggly line saying that that

edge is gone i can’t actually erase that because this is a i guess i could draw white over it but

you would still see that the blue lines are covered so the five and three connection is

gone now how do

and three connection is gone now how do we do that in inside the adjacency matrix again just look at

the uh row five column three change that one to a zero and then row three column five change that

also to a zero oops not a nine that’s how you get rid of something so you add something uh by just

changing a number you get rid of something by just changing a number self connects are pretty easy

um and then of course after you make the matrix you want to just double check that you did it

correctly I’m not going to do that right now

check that you did it correctly i’m not going to do that right now maybe this is a good exercise

for you at home you can just kind of like look and try to find my mistakes because that’s hilarious

right um what else can i tell you uh this particular scheme does not support um parallel

edges or edges that start at the same start node and end at the same end node as well i’m not

really describing that very well so for example what if i had this three node that is connected

to the 2 node and I want it

that is connected to the two node and I wanted to add a second connection for some reason like

there are reasons to do that I want to have another edge going from three to two and from

two to three so now this is a parallel edge it’s the same it’s an edge that connects the same two

nodes as some other edge how can I represent that inside of this matrix right now I can’t

but one way to do this is to say that every cell where’s the three and the two there it is every

cell in your matrix is not a one or a zero integer but every cell

or a zero integer but every cell is its own uh individual linked list or array or vector or

something that can hold multiple numbers so just to add a little notation here if if that’s what

i mean then i can say well we’ll just say that there are two edges by saying that cell has an

array of two numbers each number representing a connection not the not the greatest way to

to represent it, but in our future

greatest way to represent it. But in our future videos, we’re going to do like directed graphs

and weighted graphs. It’ll make a little bit more sense. But long story short, this is how you do it.

Let’s see. We did 20 minutes for this video. I think I’m feeling okay. There’s lots of properties

and other stuff that we can talk about with graphs. But for now, I’m just going to stop right

here. Thank you so much for watching this video. I hope you learned a little bit of stuff and had

a little bit of fun. Tell your friends and I’ll see you in the next video.

next video how do i stop the recording hey everybody thanks for watching this video again

from the bottom of my heart i really appreciate it i do hope you did learn something and have some

fun if you could do me a please a small little favor could you please subscribe and follow this

channel or these videos or whatever it is you do on the current social media website that you’re

looking at right now it would really mean the world to me and it’ll help make more videos

and

help make more videos and grow this community so we’ll be able to do more videos longer videos

better videos or just i’ll be able to keep making videos in general so please do do me a kindness

and uh and subscribe you know sometimes i’m sleeping in the middle of the night and i just

wake up because i know somebody subscribed or followed it just wakes me up and i get filled

with joy that’s exactly what happens every single time so you could do it as a nice favor to me or

you could you could troll me if you want to just wake me up in the middle of the night just

just subscribe and then I’ll just wake up.

and then i’ll i’ll just wake up i promise that’s what will happen also uh if you look at the middle

of the screen right now you should see a qr code which you can scan in order to go to the website

which i think is also named somewhere at the bottom of this video and it’ll take you to my

main website where you can just kind of like see all the videos i published and the services and

tutorials and things that i offer and all that good stuff and uh if you have a suggestion for uh

clarifications or erratics

uh, clarifications or errata or just future videos that you want to see, please leave a comment. Or

if you just want to say, Hey, what’s up, what’s going on? You know, just send me a comment,

whatever. I also wake up for those in the middle of the night. I get, I wake up in a cold sweat

and I’m like, it would really, it would really mean the world to me. I would really appreciate

it. So again, thank you so much for watching this video and, um, enjoy the cool music as,

coming for us all.

Thanks for watching!

The post How to Represent an Undirected Unweighted Graph with an Adjacency Matrix appeared first on NeuralLantern.com.

Directed Weighted Graph Edge List Representation

mike — Sun, 13 Sep 2026 19:29:05 +0000

Learn how to represent a directed and weighted graph using an edge list.

We start from a directed unweighted example, add weights to every edge, then store the graph as a tuple of a vertex list and an edge list. Each edge is a tuple of start node, end node, and weight. Order matters because the graph is directed.

Then we convert node values to indexes so you can jump straight to a vertex in constant time instead of scanning the vertex list. That keeps edge scans closer to O(E) instead of O(E + V).

This is part of a series covering all four combinations: directed vs undirected and weighted vs unweighted. Watch the earlier videos for basic graph terms and the other representations.

Leave a comment if you want a topic covered next.

00:00 Intro to directed weighted edge lists
01:05 Starting from the directed unweighted graph
01:35 Adding a weight to every edge
02:48 Graph as a vertex list plus edge list
03:35 Writing the vertex list
04:18 Node classes versus raw values
05:18 Writing directed weighted edges
05:45 Order matters on directed edges
06:38 Walking remaining outgoing edges
09:08 Why value-based edges scan slowly
10:29 Replacing node values with indexes
12:36 Constant-time jumps after an edge scan
14:13 Series wrap-up
14:45 Subscribe and outro

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hello there! Let’s talk about representing a directed and weighted

graph inside your machine using an edge list representation.

That’s a lot of words, a lot of words. Okay, so I hope you watched my previous videos. You didn’t

necessarily need to watch the previous three where we talked about edge list

representation.

where we talked about edgeless representation on the other types of graphs we’re doing a directed

versus uh undirected and weighted versus unweighted and all four combinations of those

so uh you don’t need to watch those others if you’re just only interested in this but it’s

probably a good idea if you watch my other graph videos because we talk about basic graph

terminology and like you know what is a graph and stuff like that but for now we’re just going to

continue um the screenshot you’re looking at right now was the last part of the last video where we

Thank you.

the last part of the last video where we did a directed unweighted graph so I’m

gonna duplicate this real fast and I’m gonna start modifying it so we can

basically just move on with our lives so this is gonna be directed and also

weighted then I’m gonna erase a whole bunch of other stuff because it’s fun to

draw again I don’t know why but it is I like to do my drawings get that and then

And I’m going to get rid of that stuff.

Okay.

that stuff okay and i’ll get rid of this because i’d like to draw it okay i probably should have

gotten rid of it first so i guess the real first thing that i’m going to do after erasing all that

stuff is add weights to all the edges remember this has to be a weighted graph so this particular

graph you’re looking at right now is directed and unweighted so we have to add weights to all of

the edges in my previous videos we talked about what is the meaning of weights you know these

could be a cost these could be like some property like in a video game

property like in a video game uh whatever you want them to mean uh these could even be classes

with like complicated values um but for now i’m going to say i don’t know maybe this is an airport

map and the weights are how much gas it takes to fly from one city to another maybe a node is a

city number six and city number 12 you want to fly between them it’s like five million jillion

gallons of gas so let me just take a look real fast and make sure that i’m not forgetting

I mean, any edge.

getting any edge every single edge should have a weight i think there were nine edges here one two

three four five six seven eight nine so i should see nine weights one two three four five six seven

eight nine okay we’re now ready to start representing this and what’s going on with

this computer okay the first thing uh that we talk about in all of these you know recent related

videos is that in an edge list representation we’ll say

edge list representation, we’ll say that our graph is a tuple, meaning just like a collection of some

things. A tuple where the first item in the tuple is a vertex list or a node list, and the second

item is an edge list. Again, in previous videos, we talked about representing paths using nodes or

using edges. So the edge list path is going to come back to haunt us where we do our edge list

graph representation, which is different than an edge list path.

path. So how do we do our vertex list? That’s going to be pretty easy for this diagram.

I’m going to say that V is equal to, oh, it’s pink. Let me change the color to be more serious.

Okay. The vertex list is going to be a collection of just all the nodes, just naming all the nodes

or having all the nodes. I’m going to say it’s a vertex list or a node list, but really you

probably want this to be a vector I’ve been saying that recently because it’s faster to

because it’s faster to jump to a particular index in a vector

than it is in an actual linked list or some other list-like data structure.

So we’ve got a vertex list.

I’m just going to name all the nodes.

So for me particularly, I like to go from left to right.

You can sort them, you can do whatever you want.

They just need to all be in there.

So I’m just going to say every node that we see in the graph

is going to end up in this vertex list.

So we’ve got 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6.

So we’ve got all the nodes in there.

another point that I’ve been making in the in these recent videos is that in real life in your

code in your in your computer you don’t really want to just have this value three here you don’t

want to have this 12 value here that the 12 value that’s just the value that the node holds I mean

if you want everything to be really fast maybe you know keep it bare bones but for me I like to

have a full node class a full vertex class and make an instance of it so I can add a whole bunch

of custom properties and function

bunch of custom properties and functionality and other stuff onto my node so that that means i

couldn’t really put an integer there i would have to put a full node so keep in mind for yourself

you probably want to try it both ways but um you probably want to want an instance of a node class

and maybe stick the instance right there in the vector or maybe make a smart pointer and so like

you allocate you know a new pointer of an instance of the class or it’s a raw pointer it’s a smart

point or whatever so just keep in mind this diagram is

So just keep in mind, this diagram is more simple than your code, but we’re just diagramming

today.

Anyway, so we put all the nodes in there.

The next thing I need to do is represent the edges.

So I’m going to put E is equal to another list.

And this probably does need to be a linked list or a list like data structure and not

a vector.

There’s not much point in jumping to an index.

I don’t know.

You could probably come up with one.

But anyway, so the edge list is going to be a list of tuples that describe one edge at

a time.

at a time so every little parenthesis that i put here that’s going to represent one edge so again

for me i like to go from left to right i’m going to start on the left node and i’m going to say

that the start node is three and remember this is a directed graph which means the order if you

looked at my previous videos the hang on the order of the nodes actually matters a lot like i can put

3 and 13 but i cannot put 13 comma 3 because the first item in the tuple is supposed to be the

The first item in the tuple is supposed to be the starting node.

And if you see, I only have like an edge going from 3 to 13.

I don’t have one going from 13 to 3.

So 13 comma 3 would be invalid.

It would be totally bad.

So I’m going to say the 3 goes out to the 13.

So the 3 comes first and the 13 is second.

And then I have to describe how much it costs.

So that’s the third item in that one particular tuple.

It’s going to be a 1 because the cost of that one particular edge is 1.

one gasoline one

one millisecond delay one time whatever so then the next item is going to be where else does the

three go to the three doesn’t go anywhere else so we’re done representing the three at least as a

start node so next up uh i’m going to look at the 13 where does the 13 go to it goes to the six it

doesn’t go to the three the three goes to 13 but this the 13 doesn’t go to the three so 13 goes to

six and it costs six because that’s the cost of the edge there’s two sixes here

the edge. There’s two 6s here, a little confusing, but that’s because one is a node and one is a

weight. The 13 does not go out anywhere else, so we’re done with the 13. I like to make, you know,

different rows for every single start node. You don’t have to do that. Next up, I’m going to look

at the 6. The 6 does not go out to the 13. The 6 does not go out to the 18. There is a connection

there, but it’s going in the other direction. The 6 goes to the 12 and also to the 15. So the 6 goes

to the 12, and that cost us $5,000.

to the 12 and that cost us five because that was the weight we assigned and the six also goes to

the 15 with a cost of i think i just wrote seven in a weird way um so we go from six to fifteen it

costs us seven and then we’re done looking at the outgoing edges of these six let me just double

check out out yes now we’re ready to move on to the uh the 12 node the 12 node has one outgoing

connection it goes out to the three did i get that wrong in the last video leave a comment

Did I get that wrong in the last video?

How to Represent Undirected Weighted Graphs Using Edge Lists

mike — Wed, 26 Aug 2026 17:23:28 +0000

In the last video we talked about representing an unweighted and undirected graph using the edge list representation inside your machine. Now let’s talk about how to do that exact same thing with undirected weighted graphs.

We start from the previous diagram and add weight costs on every single edge. The graph is a tuple consisting of a vertex list and an edge list. Vertices are listed from left to right. Edges are stored as triples with starting node, ending node, and weight.

We build the edge list by scanning nodes left to right so each undirected edge appears only once. Then we convert the representation to use indexes instead of node values. This lets you jump to any node in constant time when using a vector or array for the vertex list.

This makes operations on edges and nodes much faster than linear scans for both. Next up: directed graphs, both unweighted and weighted.

0:00 Introduction to Weighted Graphs
1:00 Adding Edge Weights
3:16 Creating the Vertex List
5:19 Building the Edge List
10:34 Completing the Value-Based List
10:44 Why Value-Based Is Slow
13:04 Converting to Index-Based
15:29 Benefits of Index Lookups
17:49 Wrap-Up and Next Videos
18:22 Thank You and Outro

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hey there! Hello there. Hey there. In the last video we talked about representing

an unweighted and undirected graph using the edge list representation inside your

machine. Now let’s talk about how to do that exact same thing with undirected

weighted graphs.

seeing on the screen right now is basically the last diagram that I drew on my previous video

where we talked about how to represent unweighted undirected graphs in the machine. You don’t

necessarily need to watch that video to understand this video but you probably want to watch a few

of my other previous graph videos to know the basics of graphs and edge lists and edge-based

paths and node-based paths and all that stuff. So for now I’m just going to continue from this

document. So let’s see, I’m going to duplicate

I’m going to duplicate this real fast I am going to just kind of modify the captions here because

we’re not going to do unweighted anywhere we’re going to say a weighted undirected graph did I

get that backwards I think sometimes people say undirected and then the weighted part after so

I’m just going to I’m just going to change it so it’s still undirected which means the edges don’t

have arrows so that’s fine but it’s going to be weighted now which means I have to assign a cost

of traveling along every single edge.

So I am going to just

so i am going to just sort of like erase a bunch of this stuff real fast erase these notations

uh you know what i’m going to erase all of this because i want you to you know see it

from start to finish okay so now i’m going to add weight costs on every single edge

um in the last video what i mentioned is that the the edge list representation of a graph in

the machine uh is basically your graph is a tuple that’s the orange you know marking

a tuple that’s the orange you know markings up here your graph is a tuple where the tuple consists

of a vertex list and also an edge list so we’ll do that from scratch together again but um let

me get the weights on there first what color do you want i don’t know i’m going to put arbitrary

numbers on all the edges just to say that every edge has a cost remember in a graph when you

travel along an edge if the edge has a weight then you consider that weight to be part of the cost

usually of traveling there so like if this was a network diagram

traveling there so like if this was a network diagram maybe these weights represent pings or

lags or bandwidth cost or something like that if this is like an airport diagram maybe the weights

represent gasoline or time or something like that so i’m going to do like four there we can repeat

weights if we really want to i’m going to line this up a little bit better that 12 looks gross

okay i think we’re okay now i have 14 all right did i forget anything raise your hand if i forgot

something

raise your hand if i forgot something oh i forgot okay did you raise your hand okay

i’m going to do the 13 and 6 uh let’s just put a 2 weight there you could put ones everywhere

if you wanted to i mean any any number is fine um also in an unweighted graph you kind of can

consider the number of hops to be a path cost which means you can kind of consider every uh

edge to just have a weight of one but for now we’re just gonna say this is the weighted graph

Okay, so the first…

okay so the first thing we need to do uh after that is make a vertex list so our vertex list

is just going to be a list of all of our vertices all of our nodes in the graph

how do we list them so for starters like we usually say vertex list but for me personally

this this particular data structure just that we’re going to type up on the bottom

i usually like to consider that a vector or an array at least because you can jump into a

Thank you.

uh because you can jump into a specific index in constant time which is really really fast if you

don’t know uh big o and time complexities check out my other videos but um it’s just really really

fast to jump to an index when you’re using an array or a vector but it’s kind of slow when

you’re using an actual linked list or some other data structure that makes you scan through it so

i’m going to say that my vertex list is actually a vector but i’ll keep calling it a list anyway

so we got the vertices uh we have to start naming them okay so the first thing is i’m going to do

we got the three there and we got the 13 and we got the 6 and the 12 and the 15 i’m just naming

all of the nodes in my graph i like to go from left to right because that makes it easier for

me to debug what i’m doing um you probably in your code i said this in the last video you probably

don’t want to store the actual value in your vertex list you probably actually want to create

an object of type node or of type vertex and give it the template data

and give it the template data type of in this case integer and then set the 13 inside of the class

it’s not as fast and memory efficient as just putting a number there but uh you know for me

i like more flexibility and i like to be able to do more powerful things with my stuff so i’m going

to say that 13 and all of the other nodes really that represents to me i made a brand new instance

of a class called node or vertex and then i set it up however i wanted and one of the things i did

set it up, we’ll stick to number 30.

things i did to set it up we’ll stick the number 13 inside of the class but for the for the diagram

it’s fine like this okay so we have our vertex list that’s the v if you’re looking at the uh

you know the v comma e the v part now we need to do the edge list so i’m going to say here’s my

edge list and we’re going to use the edge list representation like i talked about in previous

videos, which is basically a tuple where one tuple describes one edge. So in our

So, in our graph that we have right now, we definitely need a starting point and an ending point.

So, let me just start by looking at the 3 node, and I want to describe one of the edges for the 3.

So, the 3 goes to the 18 and the 13 and the 12.

I’m going to scan my eyes from left to right to make it a little more simple.

So, the 3 node, it connects to the 13 node, so I’m going to put a 3, 13.

the nodes doesn’t matter in an undirected graph so i could have easily put 13 and 3 it’s fine

you don’t want to duplicate it by putting 13 comma 3 sorry you don’t want to put 3 comma 13 and then

later put 13 comma 3. you don’t want to double it up because that would be like representing two

separate edges i’m just going to sort it in my mind before so that i don’t have to sort it again

later when i’m reading the graph which makes it faster for read operations but so 3 goes to 13

And then we have to represent the weight, so the tuple gets a little more complicated.

so the tuple gets a little more complicated than the last video just by a little bit i’m going to

say 3 comma 13 comma the weight which is just a 1 here and i think i mentioned this in my other

videos like a while back but uh the weight doesn’t have to be integer it could be a float it could be

any data type you wanted really as long as your algorithms support it and you have you know your

operator overloads all done and all that could be a full class just for the weight if you wanted to

but for this video it’s just going to be the weight is an integer so that’s the cost of

traveling

is an integer so that’s the cost of traveling along that one edge so notice how all of our

tuples have three items each it’s a triple tuple so i’m going to continue trying to represent uh

what the three touches so the three uh it touches the 13 and it also touches the 12 so i’m going to

say 3 goes to 12. what does that edge cost it costs us six because that’s the little pink six

there we’re done with that tuple so what else does three touch uh touches the 13 and then it touches

the

touches the 13 and then it touches the uh 12 and then it touches the 18. so i’m going to put an 18

there what does that edge cost it costs a four because there’s a pink little four at the very

top of the graph surprise you didn’t know that okay so then uh i’m sorry we’re going to move on

to the next node so we did the three already so i’m done with that i’m going to look at the 13.

where does the 13 connect it connects to the three but that’s to the left

because i’m this is why i like to scan my eyes from left to right i already know stuff on the

left is handled i don’t have to do it again so forget about the three i already described it

up here in the very first tuple three comma thirteen comma one i don’t want to describe it

again so forget about the three now the thirteen connects to the six so thirteen comma six and what

does that cost it costed two for our arbitrary labeling thirteen doesn’t touch any other node

so we’re done with the thirteen row and by the way i’m doing a line new lines here you don’t have to

to do that, I just

here you don’t have to do that i just like to i like to do one you know row per per start node

to make it look cooler and nicer okay so the uh 13 is done now let’s do the six

six touches the 13 but remember in the previous row we just handled that so i’m not going to do

it again the six to the right touches three other nodes you can see there are three lines

protruding on the right side of the six so um i’m just going to take those from left to right

It’s.

I’m just going to take those from left to right.

It’s touching the 12 at a cost of 14.

The 6 is also touching the 15 at a cost of 12, I think.

And the 6, you know, if I make mistakes, just leave it in a comment.

I will leave the video up so you can always remember my humiliation.

But I’m going to try my best.

I did not practice this.

6 touches the 15, and then the 6 touches the 18.

So 6 touches 18, and then it costs 9.

So now we’re probably done with the 6.

we’re probably done with the six um moving on uh one node to the right now we’re going to look at

the 12 okay so the 12 it touches 3 and 13 and 6 but those are already handled so forget it

the 12 touches the 15 we did not handle that right yeah because we’re going from left to right

uh and and then it costs us from going from 12 what am i doing it doesn’t touch the 15 oh my god

so the 12 touches the

uh so the 12 touches the uh the three which is already handled and it touches the

six which is already handled and then it only goes to the right to the 18. okay

anyway you know when i make mistakes on camera and i say do over i always go i don’t know why

so the 12 and the 18 uh it’s going to cost us three so then we’re done with the 12th so i’m

I’m going to go to the next one. We’ll look at the 15. The 15. 6 is already handled. 8.

6 is already handled, 18 is not handled yet, so I’m going to put 18 there, and it cost us $88, and then the 18 is the last one.

There’s nothing to do, because every node is on the left of the 18.

If you carefully, if you pause the video and look at every single node, you’ll see it’s already represented in a previous node.

So we’re officially done with the basic edge list representation of this graph, this undirected but weighted graph.

We need to do something else, though.

we need to do something else though i mentioned in the last video i’m going to repeat it in case

you didn’t watch the last video but we need to make sure that uh oh i guess i forgot to separate

those two things that means i have to duplicate the vertex list over here on the right side too

okay um so on the left this is okay but it’s kind of slow because what if we’re trying to look at uh

you know one particular edge let’s say that we we want to see what’s going on with this uh this

edge right here. Let’s say the 3 and the 13 edge, for whatever reason.

13 edge for whatever reason um i don’t know green 3 and the 13 edge okay so we’re looking at that

edge maybe for some reason we had just finished scanning uh maybe that’s not a fun edge well

what’s going on hello uh oh i forgot to set up a thing where you can make your cursor really

visible okay um actually so so this is not the most fun edge let me let me see about the 15 and

and 18-inch.

18 edge excuse me i had to take a drink of water so we’re going to look at this edge connecting

the 15 and the 18 node that’s a little more interesting so you can imagine maybe you were

doing a little scan uh if you know big o complexity by now we had to check out every single edge in

this edge list until we found the one that connected the 15 and the 18 so this was a linear

time scan based on the number of edges so this is just it’s scalable but it’s not very fast right so

We ended up kind of looking at this one.

so we ended up kind of looking at this one right here not fast um but what if we want to examine

uh some properties of the nodes or the vertices uh involved like the 15 and the 18.

here in this representation on the left we have the values we have the 15 value and the 18 value

we don’t really have a pointer to a full node object if that’s what you’re doing in your code

so um how do we get those those node objects we’re gonna have to do another linear scan we’re gonna

I’m gonna have to look at this one right here.

to look at this one right here oh that doesn’t match the value of 15 look at this one look at

this one look at this one we’re gonna have to scan every single node until we realize that it’s those

two at the end this is true even if it’s a vector uh holding your vertices because if we don’t know

the index then we have to actually just sweep through the whole vector so that’s really slow

it’s still kind of scalable but uh it’s not the best instead let’s update the the representation

on the right to have index

on the right to have indexes we did this in the last video but basically if you just kind of look

at this three node here the three node well let me let me copy this one more time the three node

corresponds to index zero which i forgot to write down my bad let me write that down for you real

fast get rid of that get rid of that get rid of that okay so i’m just going to update this vertex

list to just show you that if we have a vector or in a

that if we have a vector or an array then every single item has an index here’s index one index

two index three and four and five and then i guess i’ll just copy paste that to the other one since

i was too dumb to make an extra separated graph there um separated item okay so the uh the 15

sorry no the 13 the 3 and the 13 i guess i got to get rid of that that’s distracting me

I guess I gotta get rid of that, that’s distracting me.

The three and the 13,

those correspond to indexes zero and one

in the vertex list, right?

So zero and one, that’s the three and the 13.

So I’m just gonna change the values,

the T-type values, to the raw indexes.

It’s gonna seem a little weird at first,

and I’m gonna leave the weight alone,

because that’s totally fine.

We’re not gonna jump to a weight,

unless maybe you had a weight list, a weight vector,

if you wanted to make instances of weights.

You could do that, I’m not gonna do it.

do that i’m not going to do it so then again the 3 is a 0 the 12 is index 3 the 3 is another 0

the 18 is index 5. i’ll just do this for every single row so the 13 here is index 1 and then

the 6 index 2 notice how i’m just looking up here at the indexes of the vertex list and i’m just

changing the node values to the indexes where the nodes actually are in the vertex list so that’s a

So two.

vertex list so that’s a 2 and then the 12 is going to be a 3 and then the 6 is also going to be a 2

and the 15 is going to be a 4 and then the 6 is going to be a 2 and 18 is going to be 5

on to the next row the 12 node is index 3 the 18 node is index 5 uh the 15 node is index 4 and the

18 node is index 5 so whoa whoa correct me if i made a typo in the comments please i’ll release

another video as a thank you.

i’ll release another video as a thank you but uh now i’ve converted the whole entire representation

on the right side to an index based uh uh you know edge list so i’m gonna do this one over

here is by value and the one on the right is by index why is the one on the right better now

remember at some point we might have been scanning to find an edge well what did i just do wrong oh i

clicked over there okay we might have been scanning to find you know some edge so we’re like

Like, subscribe, and hit the bell icon to be notified when I post a new video. Thanks for watching, and I’ll see you in the next one.

Bye-bye.

edge so we’re like scanning scanning scanning scanning and then maybe we decide we’re trying

to figure out what’s going on with the two and the not the two and the four the uh the six and

the fifteen node right so that’s uh the six and the fifteen node that’s basically you know this

right here uh so now what if we want to do something with the nodes we want to do something

with the six node do something with the 15 node we don’t want to scan through the vertex list again

we don’t want to go scan scan scan scan scan that’s linear time that’s not as fast as it could

Could be.

That’s linear time, that’s not as fast as it could be.

So instead, we’ve already converted here so that we have indexes.

So if I look at the 2 and the 4, the 2 and the 4 represent indexes, not node values.

So this 2 tells me that I can go to index 2 to get the 6 node,

and the 4 tells me I can go to index 4 to get the 15 node.

Notice how I did not have to scan the vertex list to figure out where those nodes are.

And if you’re using a vector for your vertex list,

list then you can jump to every index in constant time so now if we were going to you know search

and do a bunch of stuff on edges we probably only had to spend linear time on the edge list but then

we only spent constant time uh to to manipulate each node whereas it would have been linear plus

linear uh in the past like on the left side that would have been uh you know if we’re going to do

stuff with with both the edges and the nodes it would have been o of linear time based on the

number of edges if we’re gonna do every

on the number of edges if we’re going to do every you know something to every single edge

plus linear time based on number of vertices but over here it’s going to be linear time of the

edges plus just constant time which basically means it’s going to be you know big o of just

the number of edges and i’m talking about a you know a fantasy scenario where we’re just going

to scan a bunch of stuff you can imagine there’s a whole bunch of different operations you could

do on a graph, and it would be very advantageous and fast.

very advantageous and fast if you could just jump to a node if you wanted to be able to manipulate

it directly um let’s see so i did i think 20 minutes already so i think this is going to be

it for for today’s video um and i’m going to do another video after this where we start working

with directed graphs so i’m going to do directed unweighted and then directed weighted so by the

time you watch all four of these videos

by the time you watch all four of these videos you’ll know how to represent all four types of

graphs in the machine okay anyway so thank you for watching this video i hope you learned a little

bit of stuff and had a little bit of fun i’ll see you next time tell your friends eat a chocolate

okay i’m outie hey everybody thanks for watching this video again from the bottom of my heart i

really appreciate it i do hope you did learn something and have some fun uh if you could do

me a please a small little favor could you please

please, a small little favor. Could you please subscribe and follow this channel or these videos

or whatever it is you do on the current social media website that you’re looking at right now?

It would really mean the world to me and it’ll help make more videos and grow this community.

So we’ll be able to do more videos, longer videos, better videos, or just I’ll be able to keep making

videos in general. So please do me a kindness and subscribe. You know, sometimes I’m sleeping

in the middle of the night and I just wake up because I know somebody subscribed.

just wake up because i know somebody subscribed or followed it just wakes me up and i get filled

with joy that’s exactly what happens every single time so you could do it as a nice favor to me or

you could you could troll me if you want to just wake me up in the middle of the night just subscribe

and then i’ll i’ll just wake up i promise that’s what will happen also uh if you look at the middle

of the screen right now you should see a qr code which you can scan in order to go to the website

which i think is also named somewhere at the bottom of this video and it’ll take you to my

main website where you can just kind of like see all the

where you can just kind of like see all the videos i published and the services and tutorials and

things that i offer and all that good stuff and uh if you have a suggestion for uh uh clarifications

or errata or just future videos that you want to see please leave a comment or if you just want to

say hey what’s up what’s going on you know just send me a comment whatever i also wake up for

those in the middle of the night i get i wake up in a cold sweat and i’m like it would really it

really mean the world to me I would really appreciate

it really mean the world to me i would really appreciate it so again thank you so much for

watching this video and enjoy the cool music as as i fade into the darkness which is coming for us all

Teksting av Nicolai Winther

Thanks for watching!

Thank you.

The post How to Represent Undirected Weighted Graphs Using Edge Lists appeared first on NeuralLantern.com.

4 Graph Types: Undirected vs Directed, Weighted vs Unweighted

mike — Mon, 06 Jul 2026 10:05:07 +0000

In this video we break down the four main types of graphs used in computer science: undirected unweighted, undirected weighted, directed unweighted, and directed weighted.

We start with the basic idea of graphs – collections of nodes (vertices) and edges – and then explore each type with clear examples. Learn how these graphs represent real-world relationships like computer networks, airport routes, road maps, and game maps.

Perfect for anyone learning data structures, algorithms, or preparing for coding interviews.

00:00 Introduction to Graphs
00:19 Basic Graph Definition
00:48 Nodes and Vertices
01:01 Empty Graph Example
01:17 Graph Implementation Concepts
02:02 Node Data and Templates
03:22 Adding Nodes
04:00 Adding Edges
04:44 What Graphs Represent
05:36 Graph Use Cases
06:56 Real-World Examples
08:35 Four Types of Graphs
08:52 Undirected Unweighted Graph
10:40 Unweighted as Unit Weights
11:40 Undirected Weighted Graph
13:32 Weighted Graph Benefits
15:52 Directed Weighted Graph
19:50 Directed Unweighted Graph
20:32 Summary of Four Graph Types
21:19 Closing and Future Videos

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hello there! Let’s talk about four different types of graphs that you can use and how they relate to computer science.

Okay, so you can see like I’ve got like a blank little graph paper up here.

I’m going to talk about graphs and just the very basic idea of graphs in general

and then show you the four different types of graphs that we have.

about how to implement graphs inside the machine, time complexities, maybe graph algorithms,

and a whole bunch of stuff, terminology, everything. Okay, so the first thing is, I guess I’m going to

assume probably most of you have sort of seen a graph before and you kind of understand a little

bit about it already, but I’ll say that a graph is basically a collection of nodes, also known as

vertices or vertexes, and edges, which are the lines that connect nodes to each other. This screen

See, this is a valid graph.

I’m not talking about the graphing paper.

It’s just an empty graph.

There’s nothing there.

So it’s still valid.

It’s just blank.

Okay, so then what I want to do is start drawing some nodes.

What are the nodes again?

Those are just vertices.

Those are just like little data structure objects you can imagine in the code.

I don’t want to get too far ahead of myself, but imagine that you have a class called graph.

This is just one way to imagine.

We have a class called graph and then a nested class inside of a graph called a node or a vertex

If you want to be more fancy

So the vertex class itself by the way

This is not always going to be the way that you actually do this in your code the other representations that we’ll talk about sooner a little bit easier, but

The vertex class itself needs to basically hold some data

Depending on your implementation it might know about who it’s connected to maybe the graph knows that instead

instead. In my implementations, the graph is going to know everything, but the vertex or the node

itself needs to hold one piece of data. That’s kind of the whole point. So I’m going to say that

the data type that these nodes hold are just integers. So I’m just going to put like a six in

here just to indicate we have one node and the templated data type that it holds is an integer.

And the specific integer for this specific node is just the number six. You can have any template

any template type if you really want to you can people put floats in there you could put a custom

custom class in there whatever you want but i just want to show you that we have a class called

vertex or node and inside of it’s got a template type maybe just to make this a little bit more

clear i’ll say you can imagine inside the vertex class uh there is a template type and we’ll call

it uh i don’t know node node value type or something and we’ll call it data and then up

I’m doing C++ up here.

We have to kind of define the whole graph class as a template class.

Now, of course, you could define the vertex class as the template class,

but if you define the graph class as a template, then it all kind of falls through.

So I’m just going to say class node value type.

And so if you’ve written template classes before in C++,

now you know that the user can instance the graph and at the same time,

specify what is the data type of the stuff that the nodes hold.

the stuff that the nodes hold.

We do the same thing for edges too,

but notice how there are no nodes that are connected to each other.

So we have no edges in this graph.

This is still a valid graph,

but we could just sort of copy a node just for fun and say,

all right, we’ve got two nodes now, two vertices.

They could have the same value if you want.

Graphs are supposed to, you know, support duplicate values in the nodes,

but I’m just going to change the value here.

This is also a valid graph.

You don’t really need edges to have a valid graph.

edges to have a valid graph. This is just something called a something called a graph that is not

connected. We’ll talk about all that terminology and how to detect it in a future video. For now,

I’m just going to say we have like a little graph here, which is kind of boring, but I’m going to

add an edge. An edge is basically just, you know, a little mini data structure that connects two

nodes. Depending on the way you represent this in the machine, which we’ll talk about in future

well, a whole bunch of different ways.

You could imagine this as a full-fledged class,

although that’s not always going to be the way that we represent an actual edge.

So imagine that we have a nested class called edge.

And inside the edge class, we’ve got, you know, some stuff.

We could have a weight, which means the cost of traveling against the edge.

We could have many other properties.

For now, I’ll just try to keep it simple.

is pretty much a collection of vertices and edges and some sort of connection.

What is a graph really for?

Some people at first think that a graph is another way to represent a database.

I’m going to erase this thing over here.

Graphs, you could sort of use them as databases,

but they’re not very good as databases because

it would be really, really slow to search through the graph

to find some piece of data that you’re looking for.

It could be like a linear time database.

better would be to take this graph and add a bunch of rules as you probably have found

in my other videos by now and turn it into a binary search tree.

A binary search tree is lightning fast.

It runs in log time.

Hash tables are faster than binary search trees, but basically a graph is always going

to be way slower than a binary search tree unless the binary search tree is severely

imbalanced.

But that’s something for another video.

Anyway, so we have a graph and it’s not a good database.

What would a graph be good for?

would a graph be good for? Well, graphs are usually pretty good to help you represent

relationships between things. For example, the six and the one, imagine the six is something,

maybe it’s a computer, maybe it’s a city, maybe it’s, I don’t know, like a train station,

and the edges could represent connections. So I’m just going to start changing these values

have some nodes just kind of hanging out off to the side, not really connected to anything.

Maybe not great for your particular use case, but like it’s a valid graph. So I’m just going to,

I’m just going to connect this and try to make this into a better graph.

That’s a little bit more interesting. So we’ve got graphs that do a whole bunch of different

things. Let me change these values real fast. I’ll maybe turn that into a 13 and turn that

So imagine that we have like a little connection here, a little connection here, maybe another

connection here and another one there.

And you know, you are allowed to have connections that sort of look weird, like going from this

six all the way around to this 13.

That’s totally valid also.

So I’ve basically just drawn a random graph, random nodes and random edges.

Imagine that every single node here is a computer in a computer network and imagine every edge

every edge which connects the nodes is just some sort of a connection let’s say a network cable

or a wi-fi signal or something like that so if you imagine it that way then this graph could

represent a network topology a bunch of computers connected together if these were cities and this

is like actually maybe these are airports in cities you could imagine a graph could represent

the relationship between different airports in which planes will fly notice on this graph just

that the uh you know the uh the city number one uh there are no flights connecting it directly to

city 44 but you could probably imagine well if we take a flight to uh from city one to city 10 and

then from city 10 to 44 then we can get from one to 44 we just have to be clever about our connecting

flights um let’s see so we could do like road maps airport maps the worldwide web is basically a graph

at least from a certain perspective electrical circuits that are connected to each other

are connected to each other even game maps what if your character is allowed to stand here in

in space number three on some map and the character is only allowed to travel to space 13 or

space 6 but not directly to space 1 well it could be a map that helps you understand where your

character can go in a game okay so that’s like the basic idea of of what a graph is and uh how it

actual four types of graphs that I’m going to go over in more detail in future videos. Let’s see,

what time is it right now? We got like 10 minutes. Okay, so I can still kind of make this fast.

So the first type of graph that we’re looking at right now is actually something called an

undirected, unweighted graph. Why is it, let’s see, let me write this down first. It’s an undirected,

undirected, unweighted graph. So why is this undirected? Because the edges don’t have direction.

If I was standing in, you know, city six and I wanted to like drive or fly or whatever

from city six to city three, then I should be able to do it because this edge that connects

them doesn’t really say that I have to go in one direction or the other. I could also go to city

three and then just walk right back or fly right back to city six. There’s no direction. So there’s

no direction. So there’s an this that’s that’s why this is an undirected graph. This is an

unweighted graph because we haven’t specified a cost for traveling along an edge. For example,

if you know, if you’re at city three here, and you want to fly to city 13, how much jet fuel

does it cost? How much time does it cost? If three is a computer and 13 is a computer,

and the edges like a network cable, like how much money does it cost to transmit the data?

transmit the data or what is the lag in milliseconds.

You know, you can represent all sorts of things with these edges,

but there’s no value on these edges,

which means there are no weights to these edges.

So that’s why this is an undirected and also unweighted graph.

Uh, the first upgrade that I want to do is just kind of show you what you can

sort of assume about an unweighted graph. This is not always true.

It just depends on who you talk to and what your application implementations are.

So imagine the node that goes from six, sorry, the edge that goes from six to one.

If it’s an unweighted graph, you could just probably imagine that every weight is just a one.

The point being that it always costs the same amount to travel along every edge,

because in an unweighted graph, we don’t differentiate between the different edges

in terms of their costs.

We could just put a bunch of ones on all these edges.

And it would still, you know, basically be considered an unweighted graph.

It depends on who you talk to.

maybe all the weights are zero, maybe all the weights are 10 or whatever.

But, you know, usually I put a one there because I’d like to imagine the cost could just be the number of hops.

So, for example, if I wanted to go from city six to city 10,

I could probably, you know, start at city six and then go to city one and then hop to city 10.

How many actual hops did I do? I did two.

I could also come up with that number by just looking at the sum of all the weights of all the edges.

all the edges. So notice how when I go from six to one, that costs me one weight or one hop. And

then when I go from one to 10, that’s another one. So if you put ones on all the edges in an

unweighted graph, then you’re kind of saying the total cost of some path is really just the number

of hops. So it’s up to you. Anyway, that’s unweighted and undirected. Let’s upgrade this

see we have an undirected and unweighted and i’m just going to duplicate this real fast and change

this to a weighted graph so undirected but also weighted and the thing is as soon as you start

putting numbers on a graph on the edges of a graph well then it’s considered weighted so even even a

graph that has all ones on all the edges you could also call that weighted but now you have the

freedom since it is considered a weighted graph to just assign different values to all the edges

to all the edges. Again, these edges are a class sometimes, or you can think of them that way

inside the graph. And the edge weights themselves are definitely considered a T type, a templated

type, which means, you know, right now I’m clearly typing integers, but you could type some other

data type. You could type floats. You could type some weird data type, like a string.

Whether or not that’s going to be useful depends on your program, you know, what you’re trying to

you know, what you’re trying to do with the graph. But let’s see, I think I’ve added custom numbers

to every single edge. So now this is definitely an undirected, but weighted graph. That’s the

second type of graph that we’re talking about. Okay, what’s what’s cool about a weighted graph?

Well, imagine again, that this is an airport map, where we’re representing relationships between,

you know, cities, like where can we fly and stuff. We’re basically saying at this point,

it’s going to cost you 44 of something.

Maybe this is a graph representing jet fuel or time or frequent flyer points or something like that.

If you consider your edges to be custom classes,

you could even put a whole bunch of different types of values in your graph at the same time

to make it a little bit more flexible.

But for now, we’ll just say there’s one templated type,

which means if we go back up to this code real fast, where was that code at?

Where was that code at?

And we had, you know, our rough idea of, you know, what the, what the graph holds, you

know, it holds like vertices and edges.

We could upgrade this just a little bit to say that there is a, an edge value type.

So I’m going to say class edge value, edge weight type, something like that.

for the edge so that I can save characters. And then here, I’ll change this to a type for the

node. This is why we call it T type. There’s like, we put the keyword template here in C++.

And then sometimes people just use T’s here for these tokens. So I’m just going to say

the type of data that a node can hold is going to be the T node. And then the type of data that

the edge could hold would be the T edge. We’ll call that data. Or we could call that weight,

because usually that data comes into play when you’re traveling along an edge, right? So there’s

traveling along an edge, right? So there’s like two different types here. Anyway, so we got an

undirected and unweighted graph. If we traveled from city six to city one, that costs us 44. But

if you look at the graph a little bit more closely, we could take the longer way around. We could say

go from six to three, and then go from three to 13. And then actually, let me change the color

to orange so that you can see there’s different paths, six to three, and then three to 13,

and then 13 to one, even though we took more hops,

and that might have been considered more expensive

in an unweighted graph,

you can see that the cost of the first path

from six to one, that’s 44.

And the cost of the second path is seven plus three,

that’s 10, and then plus nine, so that’s 19.

So if we take the long way,

it actually costs us less

of whatever we’ve determined this unit is.

You know, less jet fuel, less time, less whatever.

less whatever these graphs in the machine are not necessarily going to be to scale because the

machine in your computer your computer doesn’t really keep track of like the physical positioning

of all these nodes and edges it just can keeps track of the relationship between the nodes and

the edges and the weights and all that stuff so two different paths that we could take to get

from six to one one of the paths is less expensive um or less time costly or just whatever and a graph

data structure can kind of help us figure that out if we’re using an algorithm that understands

weights okay so undirected and unweighted let’s add direction so um i’m going to erase this stuff

right here real quick and in an undirected graph remember you can just kind of go in either

direction along any edge but in a directed graph every single edge needs to have a direction so as

I change one of the edges to have direction, then I must change all of the edges to have direction

as well. So I’m just saying, okay, as soon as I did that, now this is an invalid graph

because some of the edges don’t have direction. So now I need to fix everything. So I just,

I’m going to arbitrarily and randomly choose a direction for every single edge like this.

And then as soon as I’m done, I’m going to deal, I guess, with that giant edge

that giant edge. So I’m going to go like that. So let’s see, all the edges seem to have direction.

Now I’m just going to hand draw an arrow on one side of this giant edge. Okay. So this is directed

and also weighted. What can we do with the directed graph? Well, it just basically tells

you which direction you’re allowed to travel in. What if you have an airport where city six can

only fly to city one, but city one, for some reason, never flies to city six. You got to take

take like the long way you got to go from city one to 13 to three to six that’s something that

a graph could help you represent what if your character in your game can only go in one direction

but not the other direction okay no problem i mean that’s pretty much it you’re only allowed

to travel in the same direction as the edge points but now we have a graph that is a lot less

flexible because for example before we used to be able to go from city uh 10 to city 44 and then

then come back again later if we wanted in the opposite direction. We can no longer do that

because this edge only goes to 10. It doesn’t even go to 44. We can’t even ever actually get to 44.

How do you sort of solve that? Well, just add another edge in the opposite direction.

In graphs, you are allowed to do something called a parallel edge,

which just basically means, you know, two edges between the same pair of nodes that just point

in the same direction. You’re also allowed to do, you know, opposite facing edges. So

edges so i just added a second edge there going from 10 to 44 and now if i was you know hanging

out in city 10 i could just go back and forth between city 10 and 44 as much as i wanted to

oh i forgot to add an edge weight for that new edge which means i wrote down an invalid graph

so i’m just going to say two so uh maybe the wind is blowing in in your favor when you’re going from

city 10 to city 44 maybe it’s blowing against you if you’re talking about city 44 to city 10 you

you know whatever but you just have to have edge uh edge weight on every single edge

okay so uh that’s directed and also weighted um and you can probably imagine previously when we

had an undirected um graph when there was just like you know one edge going between uh two nodes

and there was no direction on it like you know 44 to 10 if we just had like one edge with no

have two edges each going in the opposite direction so we have directed and weighted i think the last

thing that we didn’t do was directed and unweighted right so we have let me just double check real

fast here we have undirected and unweighted and then we had undirected and weighted and then

directed and weighted okay so now let’s do um i’m getting lost already oh my gosh i can’t believe i

I saw undirected and unweighted so we did undirected twice already undirected so we’re

going to do directed and unweighted next okay so the next graph a little bit less useful than

what we’re looking at this this type of graph is a little bit more useful we’re going to do

directed and unweighted oh my god okay directed and unweighted so directed and unweighted you

Directed and unweighted, you can imagine, just means we get rid of all these weights.

And then we keep the direction on all the edges.

So this means we can keep track of where we’re allowed to go, if we’re pathfinding or just whatever.

But we don’t really know what it costs to travel between the different graphs.

So that’s directed and unweighted.

Let’s see here.

I’m going to just duplicate this or just make a new blank slide.

Okay, undirected, oh gosh, I’ve got pink letters.

Let’s see, undirected plus unweighted.

And we’ve got undirected plus weighted.

And then we’ve got directed plus unweighted.

I don’t think I’m writing these down in the same order,

but that’s okay.

And then we’ve got directed plus weighted.

So basically, you know, four types of graphs

that we can talk about.

In future videos, we’re going to go over graphs

in more detail.

We’ll talk about graph terminology,

maybe some pathfinding algorithms.

And yeah, so this is just a basic intro.

How much time do we spend already?

Oh God, we spent so much time.

Spent like 22 minutes.

Dang, man, even the smallest thing takes time.

So I’ll see you in a future video

when we talk more and more and more about graphs

and other data structures concepts.

Thanks for watching this video.

I hope you learned a little bit of stuff

I hope you learned a little bit of stuff and had a little bit of fun.

I’m out of here.

Go.

Hey, everybody.

Thanks for watching this video again from the bottom of my heart.

I really appreciate it.

I do hope you did learn something and have some fun.

If you could do me a please, a small little favor,

could you please subscribe and follow this channel or these videos

or whatever it is you do on the current social media website that you’re looking at right now,

it would really mean the world to me.

And it’ll help make more videos and grow this community.

So we’ll be able to do more videos, longer videos, better videos,

or just I’ll be able to keep making videos in general.

So please do me a kindness and subscribe.

You know, sometimes I’m sleeping in the middle of the night

and I just wake up because I know somebody subscribed or followed.

It just wakes me up and I get filled with joy.

That’s exactly what happens every single time.

So you could do it as a nice favor to me or you could you control me if you want to just wake me up in the middle

And I just subscribe and then I’ll just wake up. I promise that’s what will happen

Also, if you look at the middle of the screen right now

You should see a QR code which you can scan in order to go to the website

which I think is also named somewhere at the bottom of this video and

It’ll take you to my main website where you can just kind of like see all the videos

I published and the services and tutorials and things that I offer and all that good stuff and

and if you have a suggestion for clarifications or errata or just future

videos that you want to see please leave a comment or if you just want to say hey

what’s up what’s going on you know just send me a comment whatever I also wake

up for those in the middle of the night I get I wake up in a cold sweat I’m like

it would really it really mean the world to me I would really appreciate it so

enjoy the cool music as as I fade into the darkness which is coming for us all.

Thank you.

I’m going to go ahead and get started.

Thank you.

Hello there.

Let’s talk about the four types of…

Hello there.

The post 4 Graph Types: Undirected vs Directed, Weighted vs Unweighted appeared first on NeuralLantern.com.

AVL Trees: Adding Linear Data and Performing Rotations

mike — Sat, 27 Jun 2026 21:16:58 +0000

Watch me build an AVL tree step by step with linear data that would normally create a terrible unbalanced BST. See insertions, balance factor calculations, and rotations in action.

Perfect follow-up to my BST and AVL intro videos.

00:00 Introduction to AVL Tree with Bad Data
00:14 Previous Videos on BST and AVL Trees
00:28 Practice Example Building Step by Step
00:50 Adding First Node 12
01:11 Adding Node 21
02:10 Adding Node 30 and First Rotation
04:03 Recomputing Balance Factors
05:08 Adding Node 38
08:03 Adding Node 42 and Second Rotation
12:51 Recomputing Balance After Rotation
14:09 Adding Node 55 and Third Rotation
18:55 Placing Unaccounted Nodes
19:21 Final Tree and Balance Factors
20:07 Conclusion and Thanks

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hey there! Let’s build an AVL self-balancing binary search tree with some really bad data.

It’s all going to work out, trust me.

Okay, so hopefully by now you’ve seen my other videos where we talked about how to define binary

search trees, how to build them, search through them, add, delete, all that stuff. And also AVL

trees. What are rotations? Why do we rotate? How does the AVL tree maintain itself? And so forth.

just going to be a practice example. In the previous video that I that I

recorded regarding AVL trees, I started off with a really long and gnarly linear

tree and then I suddenly turned on AVLness and we rotated the crap out of

it for about 30 minutes until it was really really good. So now I’m just

going to build a tree one step at a time. Suppose for the sake of argument that

you have some really bad data. You know a long time ago, I love telling this story.

time ago you know my grandma before she passed on she was kind of bitter and she had some enemies in

the neighborhood she used to call the cops on her neighbors for gossip um she had a neighbor who

kind of feuded with her and at one point according to my grandma anyway uh my neighbor like didn’t

like my grandma’s tree and so one day when my grandma was looking out into the backyard

through the back window because she likes to yell at ducks who are swimming in her pool

notice that the other little old lady’s arm just kind of went over my grandma’s fence

with a spray bottle and then sprayed her tree. And then my grandma’s tree died. So this kind of

thing I like to call, you know, tree poisoning or data poisoning or bad data, it can affect a binary

search tree and make it really, really, really slow. But in AVL trees, if we have bad data,

it should actually end up being fine. So I’m just going to say we’re poisoning our grandma’s tree

grandma’s tree with some bad data. I’ll just do maybe maybe five pieces of data. We could go

further than that but it’s it’s going to be a super long video if we do. So we’re going to add

these pieces of data one by one. So that means the first thing I’m going to do remember we are kind

of just regularly you know building a regular binary search tree. It’s just that the differences

after we modify the topology in some way we’ll just check to see that it satisfies the rules of

then we’re going to start performing rotations to make sure that it’s self-balancing.

So we’ll add the 12 first.

So let me see if I can draw a little arrow just indicating,

yeah, we’re going to add this number right now.

I’m going to do an ellipse for a node.

And you know, like for binary, what is that?

Flying saucer for binary search trees.

It’s like, well, if there is no data already, if the tree is empty,

first piece of data you add is going to end up being the root node. So that’s it. We have our

root node here. See my other videos if you want more practice on building trees. So we’re just

going to call that the root node. And then we’re going to compute its balance factor, which is

obviously just going to be a zero. So that was super easy. Now we’re going to move on to adding

the next piece of data. Things are getting a little bit worse. This is going to be a linear tree.

tree if it weren’t for our trusty I guess AVL functionality so the 21 I’m

gonna maybe just duplicate this node right now and set that to a 21 and then

we’ll figure out where does the 21 go well it can’t be the root because the

root is already occupied 21 is larger than 12 so it’s got to be on the right

side so the 21 is going to be the right child of the root node so I’m just going

Connecting line right here.

And then we have to recompute balance factors.

So the 21 is the thing we just added.

We have to compute that.

Then we have to work our way up the tree until we hit root.

So we see the root node.

It now has a balance factor of 1.

So it got a little bit worse.

But we don’t see 2 or worse.

So that means this is currently a valid AVL tree.

And we don’t have to do any rotations.

So now it’s time to add the 30.

just realized I could just upload like a hundred videos like this and I think you’d all be pretty

happy or some people would be pretty happy um I don’t know if I want to do that to myself maybe

I will so we’re going to add the 30 node uh so first I’m just going to duplicate some node

and I’m going to call it 30 then we have to figure out where the 30 node belongs uh it’s not going

to be the root node that’s already occupied 30 belongs on the right side of 12 but we can’t use

of 12 but we can’t use that right child it’s occupied 30 belongs on the right side of 21

so you know it makes sense we called this linear data that would make a linear tree so everything

ended up being on the right side so far it’s just getting worse and worse but now the ablness is

going to kind of come to the rescue we have to recompute the balance factors so the 30 has a 0

the 21 ends up having a 1 again if you want practice computing balance factors see my other

The 12 has a balance factor of 2 and now we know right away this is not a valid ABL tree anymore

because we have a balance factor that is bad. It’s too bad.

So we have to now select an XYZ trinode subtree so we can perform a rotation.

I’m sure you can imagine it’s just going to end up being three nodes that are perfectly balanced like that.

But let’s do it one step at a time.

So the Z node is going to be the 12.

That was the first node that we noticed that was out of whack or like I guess the highest node.

or like I guess the highest node of the lowest nodes.

And then we have to find Y by taking a child of Z.

There’s only one possible child we could choose, so that’s going to be Y.

And then we find X by taking a child of Y.

There’s only one choice again, so it’s just going to be there.

Now we have X, Y, and Z, and I’m going to write it down real fast.

Let me just put this in black ink.

So X is 30, and Y is 21, and Z is 12.

Then we’re going to do A and B and C, which are going to be just in order representations of

XYZ. So again, think in your code, you would be doing pointers, you’d probably want to make three

more pointers, call them ABC. If you had a rotation function, the rotation function,

after you selected three nodes to rotate, it would receive XYZ. And then you say, let’s reorder,

you know, XYZ and call them ABC. So A is going to be 12, and B is going to be 21,

it should you know ascend from left to right if we’re not supporting duplicates in our tree

and then i’m going to um just you know make some make some nodes for our target pattern here

our output pattern so i’m going to like make some nodes here kind of place them uh in the perfect

avl tree output pattern a perfectly balanced trinode subtree i’m just going to reconnect this

The output pattern is always the same.

You know, it always starts this way because this is better

than the linear pattern that we have above.

And then I just have to update the numbers.

So the left child is going to be 12.

The right child is going to be 21.

Sorry, the center is going to be 21, the new parent.

And the right child is going to be 30.

Okay, now we look for any nodes that are children of the input nodes

that have been unaccounted for.

You can tell easily that all nodes are being used.

So we don’t even have to worry about that step.

So now that we have our trinode subtree which is perfectly balanced, we are ready to just sort of override it into the diagram.

And since the diagram only has the three nodes to begin with, I could pretty much just like erase everything, call it a day, and say this is the new tree, the new rotated tree.

So I’m just going to maybe put this in the middle I guess.

I’m going to delete this over here and recompute the balance factors.

a zero, get zeros, and this 21 also gets a zero because it’s perfectly balanced.

Next thing is let’s move on to adding the number 38. So we’ll add the 38 here and

same thing that we do before. Let’s make a copy of one of the nodes for our diagram.

Let’s call it the 38 and then let’s figure out where it belongs. It’s not going to be the new

root node because that’s occupied. It belongs on the right side. It’s not going to be the right

It’s not going to be the right child because that’s occupied.

It belongs on the right side of the 30.

It couldn’t go on the left.

That would be an invalid binary search tree.

So I’m just going to stick it right there and do a connection.

And then we’re going to update the balance factors.

So the 38 is a leaf.

It gets 0.

The 30 gets a 1.

And the 21 also gets a 1 because its left subtree is a 1 and its right subtree is 2,

or height, and the difference is just 1.

is just one. Remember we don’t really need to update the 12 or any nodes that are not

directly above the node that we just added or removed. So if you look at this tree there’s

a little bit of imbalance but nothing is two or worse so we don’t actually need to perform a

rotation. This is already a valid AVL tree. So I’m going to move on to adding the next number.

Let’s add a 42. Same thing we’re going to duplicate a node for our diagram and we’re going to call it

going to call it the 42 where does it belong well we start by looking at root that’s occupied 42

belongs on the right side of 21 the right child is occupied 42 belongs on the right side belongs on

the right side i mean it’s always going to be on the very right of the of the diagram because that’s

the poison data that we received uh so i’m going to put it over there and then connect um the child

child relationship and then let’s update the the balance factor so 42 gets a 0

38 gets a 1 and 30 gets a 2 now because it’s got 2 height of subtree on its

right side and no subtree on its left side the 21 we should update left subtree

is a 1 right subtree is a 3 oh it’s still gonna it’s actually gonna be 2 so

we have two instances of the number 2 and again which one do we actually want

by the way here’s here’s how I like to eyeball it you can kind of see oh there’s two levels of

difference in terms of the root node which one do we rotate first well as low as possible because

if we rotate the 30 it might end up fixing the 21 so we don’t want to do any more more work than we

have to so I’m just going to maybe move this over here a little bit and select our xyz um hang on

a second I think I just like didn’t do a snap to grid when I was doing that okay hang on

doing that okay hang on okay so we got to choose our x y and z uh we’re going to say that the 30

is z the lowest node possible that is out of whack and then we hop down to a child of z to find y

we hop down to a child of y to find x and so now we have our xyz i’m just going to write them down

I’m going to change the ink real fast and then we have to get ABC so A is the least value B is the

one that belongs in the middle and C is 42 now we have our ABC we’re ready to draw our output pattern

or target pattern so I’m just going to put like some nodes up here duplicate that a couple times

all right not the prettiest but I’ll take it I’m gonna do my connecting lines

and then I have to update the numbers so a is 30 and then b is 38 and c is 42 still so we’ll just

leave that as is now we have to look for children of any of the output pattern nodes that are

for so we’ll first look at the z node here the 30 it had a right child of 38 that’s already handled

as the y node so we don’t need to worry about the 38 okay next we look at the uh y node it had a

right child of 42 that’s also handled in the output pattern so we don’t have to worry about that uh

then the 42 had no children so we don’t need to really do anything this is going to be super easy

Just as a reminder, the Z could have had a left child, the Y could have had a left child,

and the X could have had two children, at least in this particular pattern.

Oh, I think in my previous video, I didn’t name off all the rotation types.

Whoops.

Okay.

So now I’m ready to just kind of like move this into the diagram.

So the 30 and 38 and 42, we can just kind of get rid of that

move the rotated output pattern into the diagram like this.

We’ll make the 38 the right child of 21.

I want to make it go a little bit more to the right

so that we have a nicely drawn diagram

so that all the nodes have space so it’s easy to debug visually.

It’s easy to just kind of eyeball it.

Then I’m going to update the balance factors.

So the 42 has 0, the 30 has 0, the 38 has 0.

Nice.

The 21, hopefully that improved.

The left subtree has a height of 1, the right subtree has a height of 2.

of one the right subtree has a height of two so actually the balance factor of the 21 node improved

to one we are now done uh rotating and we have a valid avl tree and uh we could have had you know

a tree that was just totally linear all the way down to the right it could have worked out that

way if we weren’t using avl trees uh and we would have had a really slow binary search tree but with

avl trees this is like you know a lot a lot faster reasonably and you can imagine if i added some

And you can imagine if I added some more data, let’s see, how long is this video?

Oh, it’s this video.

It’s already 15 minutes.

Let’s add one more piece of data just for fun, Zars.

I’m going to add 55.

Anybody remember that old song, I Can’t Drive, 55?

So we’re going to add the 55.

I’m going to say, here it is.

And then I’m going to do just like a new node duplicate.

node duplicate. I’m going to stick a 55 in there. And then where does the 55 belong? Well,

it’s not going to go with the root node belongs on the right side. Not going to go there belongs

on the right side, not going to go there belongs on the right side, we just end up going all the

way to the right. Pretty much. Okay, so I’m going to say it belongs there. And I’m going to connect

it. And then we update the balance factors. So zero here, and then the 42 becomes a one and the

42 becomes a 1 and the 38 becomes a 1 and the 21 becomes a 1 on the left and 3 on the right

which means we have a balance factor of 2 so now the 21 node is imbalanced this is no longer a

valid abl tree we got to rotate to make it better so once again we look at the first node that’s out

of whack or the lowest node that’s out of whack it’s going to be the 21 we call it our z and then

we find a child of z with the tallest subtree so it you know is it going to be the 12 or the 38

the 12 or the 38 it’s definitely going to be the 38 because 38 is the taller subtree same thing to

find x it’s got to be a child of y should we go left or should we go right we have to go right

because that’s the taller subtree so now we have our x y and z um i think i’ve been forgetting to

is 38, Z is 21, X, Y, and Z, and then we do A and B and C. So A is the least value, 21, B is the one

that belongs in the middle, C is the one that belongs on the right side. Now we’re ready to

draw our target output pattern. So I’m going to do this, a little duplication.

Do you like when I say, oh, we’re going to do this, we’re going to do this, we’re going to do this?

Because sometimes I just go, I don’t like it.

And I don’t think people like it when I say that.

Okay.

I’m going to connect these real fast and then change the numbers to match.

I think I made that one.

I think it’s okay.

I can never tell if it’s perfectly symmetrical.

I can’t do it.

It’s perfectly symmetric.

All right.

So A is going to be on the left.

Alright, so A is going to be on the left, that’s 21.

B is in the middle, that’s 38.

C is on the right, that’s 42.

Then we have to look for children of the output pattern that are unaccounted for.

So we’re going to do, look at the Z node.

The Z node had 12, which is unaccounted for as a left child.

So I’m going to copy the 12 somewhere.

We’ll deal with it in a second.

Then we look for the right child of 21, that’s a 38.

that’s a 38 that’s already in the output pattern so we don’t have to worry about that anymore

and then we look at the y node so y had left child was 30 that’s not accounted for so i’m

going to copy that put it somewhere else and then its right child was 42 that’s already

handled in the output pattern so we’re done there i’m going to duplicate this and then we look at

the uh we look at the x node the 42 it had a right child of 55 that also was not accounted for so i’m

for so I’m gonna just copy it over here and we’ll do something with it okay we’re done looking for

unaccounted for children again if you are just rearranging pointers you don’t really have to

worry about this in your code but since we’re doing a diagram we have to double check that

none of these nodes at the bottom here the unaccounted for children have children of their

own if they did the children would have to come with them so 55 uh no children 12 no children 30

So those are fine. If there were any children underneath, they would just stay on those nodes.

So now we have to figure out who goes where. So the 12 is the least value. That means it’s going

to go probably in the leftmost position compared to the other ones. But if we figure out like,

where does this belong in the binary search tree? It belongs right here as the left child of 21.

The 30 node, same thing. Where does it belong? It belongs between the 21 and 38. That’s the only

And then the 55, it belongs on the right side of 42 for the same reason.

Okay, I’m going to do my connecting lines real fast.

If I don’t do my connecting lines, then I don’t like it.

So now we have how many nodes in the output pattern?

We have one, two, three, four, five, six.

there’s also just six which means the final tree after rotation is just everything that we’ve

written on the right side so i’m just going to erase all of this stuff get rid of that too

and then move all these nodes over to the left call that the tree this is now the tree and then

i just have to recompute the balance factors to make sure that everything is okay so the leaves

0, 0, the 42 gets a 1, the 21 is perfectly balanced so that gets a 0.

The 38 is also perfectly balanced.

Again, it’s not about weight or mass even though there are more nodes on the left subtree,

it’s all about the height.

The height of the left subtree is 2, the height of the right subtree is 2, so 38 is actually

perfectly balanced.

Because there are no nodes that have a balance factor of 2 or worse, we are done rotating

this tree.

This is a valid AVL tree and it’s pretty fast.

So I think that’s pretty much it.

That’s all I wanted to go through today for this video.

Thank you so much for following along.

I hope you learned a little bit of stuff and had a little bit of fun.

And I will see you in the next video.

Have a great night and or day and or week and or weekend.

Hey everybody.

Thanks for watching this video again from the bottom of my heart.

I really appreciate it.

of my heart I really appreciate it I do hope you did learn something and have

some fun if you could do me a please a small little favor could you please

subscribe and follow this channel or these videos or whatever it is you do on

the current social media website that you’re looking at right now it would

really mean the world to me and it’ll help make more videos and grow this

community so we’ll be able to do more videos longer videos better videos or

just I’ll be able to keep making videos in general so please do do me a

do me a kindness and uh and subscribe you know sometimes i’m sleeping in the middle of the night

and i just wake up because i know somebody subscribed or followed it just wakes me up and

i get filled with joy that’s exactly what happens every single time so you could do it as a nice

favor to me or you could you could troll me if you want to just wake me up in the middle of the

night just subscribe and then i’ll i’ll just wake up i promise that’s what will happen also uh if

you look at the middle of the screen right now you should see a qr code which you can scan

to go to the website which i think is also named somewhere at the bottom of this video

and it’ll take you to my main website where you can just kind of like see all the videos i published

and the services and tutorials and things that i offer and all that good stuff and uh

if you have a suggestion for uh uh clarifications or errata or just future videos that you want to

see please leave a comment or if you just want to say hey what’s up what’s going on you know just

wake up for those in the middle of the night i get i wake up in a cold sweat and i’m like

it would really it really mean the world to me i would really appreciate it so again thank you so

much for watching this video and um enjoy the cool music as as i fade into the darkness which is

coming for us all

Thank you.

It should all work out according to plan, trust me.

Anyway, um, so…

The post AVL Trees: Adding Linear Data and Performing Rotations appeared first on NeuralLantern.com.

How to Perform AVL Tree Rotations – Step By Step Example

mike — Mon, 08 Jun 2026 03:26:17 +0000

In this video we walk through a real example of maintaining an AVL tree by performing a rotation. We start with an unbalanced tree, compute balance factors, identify the Z Y and X nodes, and apply a double right rotation to restore balance. Perfect follow-up if you’ve seen the basics of binary search trees and AVL trees.

Watch as we turn an invalid AVL tree into a perfectly balanced one with clear step-by-step instructions.

If you’re learning data structures and algorithms, this practical example will help you understand when and how to rotate.

00:00 Introduction to AVL Tree Rotation
00:14 Prerequisites and Previous Videos
00:36 AVL Trees Overview
00:40 Types of Rotations and Balance Factors
01:01 Examining the Example Tree
01:24 Confirming Binary Search Tree Properties
01:27 Computing Balance Factors
01:39 Identifying Imbalance at Node 65
02:01 Locating the Z Node
02:54 Finding Y and X Nodes
04:08 Assigning X Y Z Values
04:33 Creating ABC In-Order Representation
04:58 Drawing the Target Rotation Pattern
05:34 Updating Node Values in Pattern
06:04 Checking Unaccounted Children
07:00 Reattaching Nodes and Performing Rotation
07:56 Recomputing Balance Factors
08:24 Updating Root Balance Factor
08:41 Resulting Perfectly Balanced Tree
08:48 Identifying Double Right Rotation
09:06 Explaining the Rotation Process
10:16 Conclusion and Next Video Teaser
11:56 Channel Promotion and Outro
15:48 Final Hello and Recap

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hey there! Let’s maintain and rotate an AVL tree which is a self-balancing binary search tree.

Okay. Alright, so hopefully by now you’ve seen my other videos. If you haven’t,

you probably won’t understand this unless you’ve seen other videos elsewhere.

But in my previous videos we talked about what is a binary search tree, how to make one, how to

binary search tree, how to make one, how to define one, how to know you’re looking at one, how to build one, search,

insert, remove all the operations and time complexities.

And then we talked about AVL trees, which are a self-balancing binary search tree.

And we talked about what are the different types of rotations you can do? Why would you rotate?

How do you compute balance factors? How do you know when it’s time to rotate?

How do you do the rotation? Stuff like that. So this is just going to be one

example tree, and we’re just going to try to burn through it. If you want to learn more about

see my previous videos. Okay, so supposing now that you have a tree that looks like this, let’s

confirm that this is a valid AVL tree. This seems to be a tree. It’s a connected graph. It’s got no

cycles. It’s a rooted tree. It’s a binary tree. There are no more than two children per every

single node. And the data is in order. So 14, 22, 36, 41, 48, 55, 65. So this is a valid binary search

Now to determine if it’s a valid AVL tree, we just have to compute balance factors.

So in my previous videos, we talked about doing this.

So I’m just going to try to burn through this quickly.

I want to put zeros on all the leaves because that’s pretty easy.

This 48 gets a 1.

The 65 actually gets a 2.

So at this point already, we know there’s something wrong with our tree.

We need to rotate it.

This is not a valid AVL tree because we see a balance factor that is worse than, you know,

plus or minus 1.

61 is going to have a balance factor of, let’s see, just a 1.

And so really the only thing that we need to rotate is going to be this 65 node.

This is the node that’s out of whack.

Sometimes you see, you know, the bad balance factor in other areas of the tree,

maybe like a little bit higher and also a little bit lower.

You want to rotate as low as possible first because sometimes when you rotate low,

it fixes stuff that’s higher.

This is actually only true if the thing that you’re rotating is a direct descendant,

Not necessarily a direct child, but just a descendant of the thing that you see that is higher if you have two different nodes that are

unrelated in terms of

You know, they’re not direct descendants or ancestors of one another. They’re sort of like siblings or cousins

Then it doesn’t really matter so much which one you rotate first because they’re not really going to affect each other

but

In this case if we rotate, you know starting with the 65 there’s a chance that the 41 will get fixed up a little bit

I haven’t tried this yet, so I don’t know for sure, but I have a feeling it might.

Let’s see what happens.

So we know that the first node that is out of balance we’ll call the Z node.

So I’m just going to put a Z here.

Let me just duplicate this and we’ll say Z.

Hang on a second.

I got some dashes in my pen.

There we go.

We’ll make this the Z node.

And then we have to find X and Y.

We’ll do that backwards.

We’ll find the Y first and then the X.

them by going down one level at a time so the Y node will be a child of Z and

we’ll have to find the child that has the taller subtree in this case there’s

no choice because there’s no subtree on the right side of 65 so we can only go

left but just keep in mind if there was a subtree let’s say like that then we

would still go to the left and select that 48 as the Y node let me just write

down Y node here because it would have a taller subtree notice the left subtree

in this little example has a height of 2 and the right subtree has a height of 1

That subtree has a height of one.

So let’s just get rid of that little extra thing.

Same thing for the X.

We want to find a child of Y and we’ll always take the taller subtree.

So you know, if there was a subtree over here and maybe like another like node down there,

then we would still go to the right to get the 55 because it would have the taller subtree.

In this case, there’s only one choice.

So the X node is just going to be this 55 and that’s it.

So let me just put an X right here.

are x and y and z i’m just going to write that down real fast x equals 55 i’m going to probably

change the color here y is equal to 48 uh z is equal to 65 um and then we want to make an in

order representation of xyz and just call it abc so i’m going to say a is equal to something

and so is c so a is going to be the least value the value that belongs on the left because again

these are supposed to have ordered data like binary search trees so i’m going to put 48 here

and 55 there and then 65 here now abc is the in order representation of xyz now that we’ve done

that i’m going to draw our target pattern here so let’s see i’m going to do i’m going to do a

to connect with some blue lines because that’s just like such a cool connection.

Hang on a second.

I put that a little bit too far down.

Okay.

So we’ll do that.

And then I’m going to do another connected in line.

Okay.

I had to make a little edit there.

So I’m going to just continue making this blue line.

So I’m going to do this.

And I have to update the values now.

the values now. So this 14 on the left, that should be the A node. So we’re going to see 48,

and then the new parent is going to be 55, and then the right child is going to be 65.

Always after you fill in these values, ask yourself, have I actually drawn a valid binary

search tree? If you haven’t, meaning if the data is out of order in some way, then you haven’t

drawn a valid binary search tree, and you probably need to try again. So we’ve got 48 and 55 and 60.

is are there any children that are unaccounted for in terms of the input nodes to the pattern

that we’ve just drawn down here, the output pattern.

So let me just kind of remind you that there could have been, you know, potentially some

nodes, right?

Like we could have had a right child of 65, we could have had a left child of 48, and

we could have had two children of 55.

So there’s always a potential for four nodes that are unaccounted for.

We’ll just check them one by one real fast here.

Look at the 48 first. The 48 had a right child of 55, but that’s already taken care of in the output pattern, so we don’t have to worry about that.

Now we look at the 55. We could go XYZ if we wanted to, but I like looking at the output pattern.

55 had no children, so that’s fine. And then we look at the 65. The 65 had a left child of 48, but that’s already in the output pattern.

So at this point, all children are accounted for. We don’t really need to do that much.

that were unaccounted for they would need to be attached under the 48 and 65 somewhere and each

child would only go in one place without an there’s only one place that the child could go

without invalidating the binary search tree but that’ll be i’m going to make a harder example in

the next video so now that we’ve done this we’re ready to reattach all the nodes are accounted for

that we’re about to remove from the diagram we’re not actually going to be deleting nodes or creating

creating nodes or anything like that in the code we’re really just disconnecting

pointers and reattaching them so I’m gonna just erase this from the diagram

but keeping in mind that the nodes are not really being recreated and I’ll just

put the 55 over here where the old trinode subtree was and then I’m gonna

recompute the balance factors for all of the nodes involved so you know I just

the output pattern someone put a 0 48 also 0 because their leaves the 55 it’s a 0 it’s perfectly

balanced that’s pretty sweet and now that we’re done with the nodes that we touched we have to

work our way up to the root node we don’t have to worry about anything over here on the left

because those nodes couldn’t possibly be affected by uh by the rotation we just did because only

nodes that are above the rotation will be affected so uh the last one we you know looked at was this

basically going to say all right 55 let’s look up one more parent it’s going to be the root node

the 41 so what’s the new balance factor of the 41 node it’s actually going to be better it’s going

to be a zero so with that in mind we’ve actually created a perfectly balanced binary search tree

this is definitely a log time tree super super fast and super super cool and what type of rotation

So we had XYZ. If you don’t have the rotations memorized, keep in mind my previous videos explain all of that with some fun ways to help you remember, hopefully. Maybe some unfun ways.

So I’ll just kind of like reiterate real fast here. There are two nodes that need to be moved into position. Notice how 55 is supposed to be the new parent node, which means the 65 needs to be rotated under the 55, and so does the 48.

And so does the 48. So the 48 and the 65 both are going to be rotated into position.

That means two nodes are rotated, which means it’s a double rotation, not a single rotation.

Which node was rotated first? I always rotate the Z node first, you know, the node on the very top.

And so I’ll just use the rotation direction of that Z node.

So that’s a regular clockwise rotation.

And that’s a right rotation, so this is a double right rotation.

you can do to remember is if you go from y to z you’re going up into the right so that’s a right

rotation you could also imagine that there is some negative space kind of sitting here on the right

side a little right pocket so that’s a right rotation and i’m sure there were some other ways

that i added in the other video but i can no longer remember them so i’ll just move on we’ll

say we did a double right rotation in order to get this uh this perfectly balanced binary search tree

research tree so I’m gonna cut the video here in the next video we’re going to I

think probably rotate a linear tree you can kind of see I’ve already started to

draw one here in the next video we’re gonna look at this like giant gnarly

linear tree and we’re gonna pretend that we have the ABL rotating disabled for a

while while we built this tree and then all at once we’re gonna turn it on and

do like a whole bunch of rotations and see what the tree is gonna end up

looking like it’s gonna be pretty ugly and fun anyway thank you so much for

Anyway, thank you so much for watching this video.

I hope you learned a little bit of stuff and you had a little bit of fun.

I’ll see you in a moment, hopefully.

Hey everybody, thanks for watching this video again from the bottom of my heart.

I really appreciate it.

I do hope you did learn something and have some fun.

If you could do me a please, a small little favor, could you please subscribe and follow

as you do on the current social media website that you’re looking at right now.

It would really mean the world to me and it’ll help make more videos and grow this community.

So we’ll be able to do more videos, longer videos, better videos, or just I’ll be able

to keep making videos in general.

So please do me a kindness and subscribe.

You know, sometimes I’m sleeping in the middle of the night and I just wake up because I

know somebody subscribed or followed.

It just wakes me up and I get filled with joy.

That’s exactly what happens every single time.

So you could do it as a nice favor to me or you could you could troll me if you want to just wake me up in the middle

And I just subscribe and then I’ll just wake up. I promise that’s what will happen

Also, uh, if you look at the middle of the screen right now

You should see a QR code which you can scan in order to go to the website

Which I think is also named somewhere at the bottom of this video

And it’ll take you to my main website where you can just kind of like see

All the videos I published and the services and tutorials and things that I offer and all that good stuff and

and uh if you have a suggestion for uh uh clarifications or errata or just future videos

that you want to see please leave a comment or if you just want to say hey what’s up what’s going on

you know just send me a comment whatever i also wake up for those in the middle of the night i

get i wake up in a cold sweat and i’m like it would really it really mean the world to me i

would really appreciate it so again thank you so much for watching this video and um enjoy the cool

Enjoy the cool music as I fade into the darkness which is coming for us all.

Thank you.

Hello there.

Hi there.

Hi there. Let’s maintain a self-balancing AVL tree,

which is recursive. Hello there. Let’s,

The post How to Perform AVL Tree Rotations – Step By Step Example appeared first on NeuralLantern.com.

AVL Tree Rotations Tutorial: Fixing Imbalance After Adding a Node

mike — Mon, 01 Jun 2026 05:46:56 +0000

In this video we walk through a complete example of maintaining an AVL tree. Starting with a valid AVL tree, we insert a new node that breaks the balance rules, then recompute balance factors up the tree until we find the imbalance.

Watch as we identify the X, Y, and Z nodes and perform a double right rotation to restore the AVL property while keeping it a valid binary search tree.

Perfect for students learning data structures, computer science fundamentals, or anyone preparing for coding interviews.

Previous videos cover binary search trees, AVL basics, rotations, and balance factors.

00:00 Intro to AVL Tree Rotation
00:20 Prerequisites and Previous Videos
01:06 Initial AVL Tree Example
01:18 Computing Balance Factors
03:44 Adding Node 54
04:31 Recomputing Balance Factors
06:08 Detecting Imbalance at Node 78
07:20 Identifying X Y Z Nodes
08:36 Labeling X Y Z and Trinode Pattern
10:09 Output Pattern and BST Ordering
11:03 Handling Extra Children Nodes
14:50 Reattaching Rotated Subtree
15:24 Recalculating Balance Factors
17:05 Double Right Rotation Explained
19:18 Final Verification and Outro

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hello there! Let’s maintain an AVL tree by rotating some nodes after we add a new node that messes up the whole tree.

Okay, I hope that before you watch this video you’ve seen my other videos where we talk about what is a binary search tree, how to define it, terminology, how to build a tree, search through the tree, all the stuff for the tree.

the tree all the stuff for the tree the binary search tree and then my other videos where we

talked about what is an avl tree what is a rotation what are the different types of rotations why would

you want to rotate how do you do the balance factors all that stuff happens in previous videos

so uh search the video history anyway so for now i’m going to assume that you know all that because

you watch the videos and now we’re looking at an a we’re looking at an avl tree maybe first we’re

a valid AVL tree and then we will add a new node which will probably mess the whole thing up

and force us to do a rotation to get the tree back in balance.

Okay so the first thing I’m going to do is just this is an example tree, it’s got some nodes

and I’m going to compute the balance factors for every single node just to double check.

Remember the rule that we’re using is if an AVL tree has a balance factor of two

for any node, then it’s considered invalid.

The tree itself is just a binary search tree,

not an AVL tree, until we fix the imbalance.

So the 44 node, wait, hang on, that’s actually wrong.

I don’t know why I even typed that number there.

Oh, because I was saying two.

First thing I want to do is do the balance factors

for the leaves, because they’re the easiest.

All the leaves have a balance factor of zero,

because they have no difference in left subtree

versus right subtree height.

The 50 node is also kind of easy,

because it’s left subtree and right subtree

left subtree and right subtree have the same height so that’s just a zero 17 is a little bit

more tricky it’s got one node hanging off the right side so its right subtree height is one

its left subtree height is zero so absolute value of zero minus one is just going to be one

so that’s not perfect but at the same time that’s acceptable we can just sort of move on remember

only two or worse is going to make us stop we look at the 78 again let me just uh or for the first

or for the first time we look at the 78 let me just do this the hard way to make sure everybody’s

on the same page uh for the for the balance factor of the 78 node we look at the height of the left

subtree uh which is two and then we look at the height of the right subtree which is one

and so if you take the absolute value of two minus one that’s going to be one

so actually the balance factor of the 78 node is okay this is maybe a good time to point out the

We don’t care that there are more nodes on the left. We just care about the height of the left subtree

So I’m going to duplicate this slide to continue so far so good every node seems to be okay

We’ll look at the 44 node. You can probably eyeball it because

Well, I mean for me when I want to eyeball a balance factors

I just look at the left subtree versus the right subtree notice how there’s like one level of difference

in height we could do it the hard way if we wanted to and

do it the hard way if we wanted to um so like the left subtree has a height of two right subtree has

a height of three so two minus three absolute value that’s going to be one or just that one

line that i drew before which was the the difference so that means this whole tree is

actually okay it is a valid avl tree nice video over i’m just kidding uh let’s add a node that

So I’m going to add the number 54.

Let me just try to select an existing node here, duplicate it.

I’ll change this to a 54.

Then we’ll figure out where the 54 node actually belongs.

Hopefully you’ve already become an expert at binary search trees.

So I’m just going to do it real quick.

We show up top here, 54 belongs on the right.

We look at the 78, it belongs on the left.

We look at the 50, it belongs on the right.

We look at the 62, it belongs on the left.

right there as the left child of the 62 node. So I’m going to go ahead and do my little connecting

line indicating that the nodes are now pointing to each other. The 54 thinks its parent is 62.

The 62 thinks its left child is 54. And now we have to recompute the balance factors.

So obviously the node we just added, it doesn’t have a balance factor, so we have to recompute

way up the tree until we hit the root node, recomputing all balance factors along the way.

We don’t actually, I’m going to do marks here to make sure that I don’t forget.

We don’t actually have to recompute, you know, the 17 or the 32 or the 88 because those nodes

are not possibly going to, or actually even the 48, because those nodes are not possibly going

to be affected by the 54 node because balance factors are only affected by nodes that are

or even nodes below wouldn’t be affected. So we’re only going to compute the 62, the 50,

the 78, and the 44, working our way up to the root node. Soon as we hit root, then we’re done

recomputing. So the balance factor for the 62, I’m going to eyeball that. That’s going to be a one

because left subtree height is one, right subtree height is zero. So far, so good. As soon as we

away. Again as I said in a previous video we probably will see that the root

nodes balance factor is bad but if we if we compute the whole tree and then just

decide I don’t know like the root node is going to be rotated we’ll probably

rotate incorrectly you want to rotate as low as possible first because rotating

lower in a tree is probably going to fix nodes that are higher. So recomputing the

balance factor for the 50 that’s going to be a 1 because left subtree height of

right subtree height of 2, take the absolute value of the difference there.

We go up to the 78 node and this one is going to be bad because you can see that the left subtree

has a height of 3 and the right subtree has a height of 1 so the bounce factor is going to be

a 2. It’s at this point since we just started by inserting the 54 and worked our way up that I

would stop and do a rotation but just for the purposes of this tutorial I’m going to compute

just to show you what’s going on.

The height of the left subtree off the root node is two,

the height of the right subtree is one, two, three, four.

So that means the balance factor of the 44 node

also has a two.

So at this point, it might be a little confusing

if you don’t remember that you kind of have to stop

as you’re working your way up

or at least rotate the lowest possible node first.

You might be confused, you know, which one do I rotate?

Do I rotate the 78 first or do they rotate the 44?

If we were to rotate the 44 first, the root node, you know, we could do it.

But at the same time, there’s a chance that it won’t actually fix the 78 node.

And there will be other stuff underneath that is bad.

And so it’ll cost us more work to do it that way.

So instead, we’re going to stop at the 78 and do our rotation.

So remember we said in a previous video that we’ll choose the first node that is out of whack as the Z node.

We’re looking for X, Y, and Z.

I’m going to write X, Y, and Z here.

X, Y, and Z.

Now, how do we choose Y?

We go down to a child of Z,

and it has to be the child that has the taller subtree.

Notice how the left subtree of the Z node has a height of 3,

and the right subtree has a height of 1,

which means we definitely need to go left to find the Y node.

So I’m going to put Y right here.

If the left and the right subtree had the same height,

then it doesn’t really matter which one you choose.

matter which one you choose. Maybe try to be consistent, but definitely we have to go left

this time because that’s the taller subtree. Again, look how tall it is. Okay, now we need to look for

the X node. Again, we have to take the left or the right child of the Y node, or just like a grand

child of the Z node. That is definitely a child of the Y node. We have to choose the taller subtree,

so we could not put X as 48. We can’t do that because that’s not the taller subtree. Instead,

Instead, the X is going to be the 62 node because that’s the taller subtree.

Now we have chosen our X, Y, and Z node,

which means I’m going to just type some stuff up here real fast.

I’m going to do X is equal to 62, Y is equal to 50,

and Z is equal to 78, just as a reminder.

And this is kind of similar to what you would do in the code.

I mean, on these diagrams, us humans,

we have to like rearrange things and name the types of rotations and so forth in the code it’s

actually really easy uh in comparison because all you have to do is produce an in-order representation

of the three node pointers that you received x y and z let’s say we have a function called rotate

we don’t even have to remember the types of rotations you just grab xyz and then you order

them and call them a b and c let’s do a equals something b equals something c equals something

So A is going to be the least value because again, this has to be a binary search tree

before it can be an AVL tree.

So 50 is going to go on the left.

That’s the only place that it could go.

And then 62 in the middle and then 78 on the right side.

And then I’m going to just, maybe I’ll copy and paste this here.

This little trinode subtree.

Was that, will that work?

Yeah.

So I don’t have to draw this again.

I’m going to erase some of this stuff.

Oh, come on, man.

I’m going to erase some of this stuff just to make it a little more neat.

just to make it a little more neat.

Then I’m going to replace the values in these nodes with just X, Y, and Z.

So, sorry, ABC.

So A is going to be 50.

That’s the leftmost node or the least value.

And then B is going to be 62.

And then C is 78.

Before you continue, make sure you’ve actually drawn a valid binary search tree,

because if you haven’t, then your AVL tree is not going to end up being valid either.

not going to end up being valid either it always has to be a valid binary search tree so the order

has to be correct so if you were thinking about well how can we can’t put the 78 in the middle

or how come we can’t put the 62 on the left what would have happened well it would have been invalid

or you would have ended up with like a straight line or something that wasn’t the target pattern

for a rotation which is supposed to be a perfectly balanced trinode subtree okay so now we’ve got x y

here which is going to basically take away from these three nodes the next thing we need to do is

take into account any nodes that come underneath nodes from the output pattern so our xyz i guess

you could say input pattern too let’s look at uh you know x for example so like the 62. did it have

any children that are not accounted for in the output pattern actually yes it has a 54 node so

this 54 needs to go somewhere we can’t just like erase it from the tree so i’m going to move it

to move it down here just so I don’t forget it. Then we look at the Y node. What children did the

Y node have? It had a 48 as a child and a 62 as a child. The 62 is actually already handled in the

output pattern so we don’t need to worry about that but the 48 was not handled so we got to put

that somewhere too. So I’m going to move that down here. Now we look at the Z node. The Z node

had 50 as a child, as a left child. That’s already handled in the output pattern so we don’t need to

don’t need to worry about that it also had 88 and that is not in the output pattern so we have to

do something with 88 so i’m going to move that down here too i should also point out um i think

in a future video i’m going to do a more complicated example where some of these nodes that are

children of the uh the output pattern they might have children of their own or descendants of their

own if they do don’t rearrange any of the descendants so anything that was below 54 just

hanging exactly where it was already off of the 54.

Same thing for the 48.

If it had any children of its own,

just leave them in place.

Don’t touch them.

Don’t touch any descendants.

So now that we’ve done this, whoops, dang it.

Let me copy this in a good way instead of a bad way.

Okay, let me erase this real fast.

X, Y, and Z.

Nope, that’s going to screw me up.

I’m going to forget.

Okay, now we have to place these nodes

nodes of the output pattern in their appropriate position like where do they

actually belong well remember this is supposed to be a binary search tree so

there’s actually only one place that the 54 node could ever go and still give us

a valid binary search tree so I mean think about it for a second could it go

on the left of 50 no could it go on the right of 62 no it has to go in between

the 50 and the 62 otherwise we wouldn’t have a valid binary search tree so I’m

there maybe a little bit lower to make this a more beautiful diagram then I’m going to do my

connecting line real fast so I’m going to do this so it’s the right child of the 50 now notice how

before it was the left child of the 62 so then you know again we’re just really disconnecting

pointers and then rearranging them so this 48 it can’t be on the right side of 62 it has to be on

the left side it can’t be on the right side of the 50 it has to be on the left side so the 48 must be

side so the 48 must be the left child of the 50. again you must end up with a valid binary search

tree or you’ve done something wrong so i’m going to just kind of do this here

um and then same thing for the 88 node there’s only one place this could go it can’t go on the

left of 62 it has to go on the right of the 78 it couldn’t go on the left of the 78 that would be bad

news so i’m just going to place this here and then uh just make a little connecting line okay

Okay, now I’m going to double check to make sure that I didn’t forget any other nodes

because when you’re working with a diagram, you might forget a couple of nodes and just

sort of like erase too many nodes without putting them in the output pattern.

If you’re rearranging pointers, it’s fine.

You wouldn’t have to worry about any nodes that came underneath these nodes because they

would just remain attached in place.

But I just want to double check real fast.

So we got X, Y, and Z.

So that’s three nodes and then four, five, six.

So we’ve got six nodes total if we include the XYZ nodes and all nodes that are direct children of those and even underneath.

So how many do I have in the output pattern?

1, 2, 3, 4, 5, 6.

So I’ve got the same number of nodes.

I’m ready to erase all this stuff up top and reattach.

1, 2, 3, 4, 5, 6.

Yeah, reattach this into the diagram.

So I’m literally just going to erase all this stuff right here.

Then I’m going to select all the nodes in the output pattern.

the output pattern and i’m going to move them up to be the new right child of the 44 because that’s

where originally the z was so i’m just going to maybe move these up here real fast and then get

that 32 back down where it belongs dang you 32 uh actually it’s a little bit too low get that

So the last step is we have to recalculate the balance factors to make sure that we have a valid AVL tree.

Maybe we have to do another rotation, maybe not, I don’t know.

Kind of looks like maybe not, but I’m not going to take any chances.

So let’s do the leaves first.

Remember, we have to recompute the balance factors for every node that we just moved.

So all the nodes in the output pattern and their immediate children, not anything lower.

all the leaves are just going to have a balance factor of zero that’s pretty easy.

The 50 is perfectly balanced nice so it’s going to have a balance factor of zero.

The 78 has one node hanging off the right and nothing on the left so it’s got a one there.

The 62 again we’re not looking at mass we’re not looking at weight we’re looking at the height of

the left subtree versus the height of the right subtree so this is actually perfectly balanced

because the height of the left subtree is 2 and so is the height of the right subtree.

we’re done with all the nodes that we just moved we should recursively or just kind of like walk

our way up the tree and recompute all balance factors until we find the root node. Okay so

there’s the root node only one more thing left to do. The balance factor of the root node is let’s

see left subtree has a height of two right subtree has a height of three so the balance factor for

the root node is going to be a number one. Notice how the 44 the root node got fixed because we

we rotate it a little bit lower.

And this is not the fastest tree in the world,

but it is considered a log tree

because the imbalance is only scaling

with a constant factor because we’re limiting

the balance factors to just the number one basically

before we rotate.

So what type of rotation did we actually perform?

If you looked at my previous video,

you should know this already,

but maybe I’ll duplicate this here

sort of start to maybe annotate it. I’m going to do…

Okay, so what is the rotation we did? Well, if we look at the ZYX here, the XYZ,

there’s a little bit of a bounce. Actually, let me do orange. There’s a little bit of a bounce,

right? So that’s going to be a double rotation. Or you can imagine that we had to move two nodes

and the 50 on the left and the 78 on the right. Notice how the 78 had to be rotated first.

So it’s like under the 62. And then the 50 was rotated second underneath. I mean,

we snipped off that 54 elsewhere. But long story short, there are two nodes that need to be rotated

into position for output pattern. So that’s a double rotation. So diagonal bounce or two nodes

means a double rotation and then is it a left or a right rotation well if you

think about the first node that we rotated it was the 78 what’s going on my

computer the first node that we rotated was 78 the Z node so what direction did

we rotate that that was clockwise so that’s a right rotation so a double

right rotation another way of looking at it is if we only look at the input

look at the input pattern we just look at you know these nodes right here there was kind of a

pocket of empty space on the right side wasn’t there so that’s why it’s a double right rotation

another way to think of it is I’m running out of colors if we started at the y node and worked our

way up to the z node we went up into the right so that’s a double right rotation also either way you

cut it we performed a rotation and now we have a pretty good tree okay let me just double check

Okay, let me just double check.

This is a valid BST.

Doop, doop, doop, doop, doop, doop, doop, doop, doop.

And it’s a valid AVL tree

because all the balance factors are okay.

Yeah, and in future videos,

we’re going to do more rotations.

I’m probably going to do at least like,

you know, two or three more videos

where we just simply rotate, you know, some tree

and explain it and work our way through it.

If you have an idea for a really gross tree

that you want me to rotate in front of you,

AVL Tree Rotation Types Explained for Self-Balancing Binary Search Trees

mike — Mon, 25 May 2026 20:03:52 +0000

Hey everyone, in this video we break down the four types of rotations you need to know for AVL trees – self-balancing binary search trees.

We cover single right rotations, single left rotations, double right rotations, and double left rotations with clear diagrams and explanations of the input patterns and how they become the balanced output pattern.

If you’ve been learning about binary search trees and want to understand how AVL trees maintain their balance through rotations, this is the perfect next step. We look at the trinode subtrees, balance factors, and exactly how to rearrange the pointers for each case.

Great for computer science students, coding interviews, or anyone building their data structures knowledge.

Watch the full series on binary search trees and AVL trees for more.

00:00 Introduction to AVL Tree Rotations
00:14 Previous Videos Overview
00:28 Balance Factors and Trinode Subtrees
00:50 Identifying Imbalance
01:56 When to Rotate
02:20 Four Input Patterns
02:41 Target Balanced Pattern
04:18 Single Right Rotation
04:33 Single Left Rotation
08:44 Double Rotations
11:51 Remembering Rotation Types
13:04 Wrapping Up Rotations
13:27 Thanks and Outro

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hey there, let’s talk about rotation types in an AVL tree, which is a self-balancing binary search tree.

Okay, so hopefully you’ve watched my previous videos. If you have not, you probably want to check them out first,

where we talk about what is a binary search tree, how to build one, how to define one,

terminology, searching through it, all that stuff. And then we talked about an introduction to AVL trees,

trees which are self-balancing binary search trees this video is going to be

about the types of rotations that you can perform in an AVL tree what do I

mean by rotation well the basic idea that we talked about in the last video

was that throughout your tree you’ll notice that different nodes have

different balance factors which means how imbalanced or balanced they are when

we identify a node that has a balance factor that’s too bad then we consider

AVL tree and we have to stop and rotate a couple of nodes you know kind of rearrange them to make

them better before we have a valid AVL tree so we have four different input patterns that we can

have so imagine you know this little trinode subtree up on the top left that could be you know

three nodes that we found somewhere in our tree that had a bad balance if you just quickly compute

the balance factor for this trinode subtree you’ll notice actually let me just do it real fast for fun

that the 65 node has a balance factor of 2 because its left subtree has a height of 2

and there is no right subtree. The 55 has a balance factor of 1 and 48 being a leaf, at

least in terms of this trinode subtree, has a balance factor of 0. All of these trinode

subtrees are going to have the same situation. The one on top is going to be 2 and so forth.

So you can imagine that you were going through the whole tree, computing balance factors like

And you found a two, which remember we said in our last video, two or worse, meaning two or higher,

if we’re using balance factors that are absolute or negative two and also positive two or worse,

if we’re not using absolute balance factors, means you got to stop and try to rebalance that trinode subtree.

So we found a node that had a balance factor of two and we realized we have to stop and rotate.

The pattern of the trino subtree before we perform the rotation could be one of these four things.

It could be the thing on the left on top, the thing on the right on top, the thing on the bottom left, and the thing on the bottom right.

And all four of these patterns should end up becoming, after we do our rotation, they should end up becoming the pattern in the middle.

So this is always going to be the target pattern.

Let me draw some arrows real fast.

pattern is going to end up looking like the output pattern in the middle.

Why is that?

How is that possible?

Well, we only have three nodes.

If you look at all the input patterns, they’re all the same numbers.

What we’re really doing is disconnecting all the pointers, disconnecting the parent child

relationships and then reconnecting them in the best possible way to make, you know,

the most balanced trinode subtree.

Notice how the height of all of these input trees is always three, right?

because it’s a trinode subtree that’s really really bad and out of whack so we’ll you know

like one two three one two three right height of three we’ll do a rotation rearrange the pointers

rearrange the parent-child relationships so that the final height ends up being actually just two

and if you think about reducing the height we’re making the tree better we’re making it more

balanced we’re making it faster to search through and add and remove things from so we’re making a

So we’re making a better tree by reducing the height a little bit.

If you had a really, really, really bad tree and you just went around to all the bad nodes

and just started rotating them all, you’re reducing the height by one for each rotation.

Eventually, when you get up to the top of the tree, you’ll have an overall AVL tree,

which is pretty fast.

We should say now that AVL trees are always going to be log time trees because the imbalance

factor is limited by a constant number.

We’ll say that again in a future video.

in a in a future video so anyway i’m going to label these trees now

i’m going to say that the one on the top left is a single right rotation

and the uh the tree on the top right you can probably imagine is a single left rotation

let me just duplicate this real fast so i can come on man can i duplicate this yeah so i can

edit the text real fast. This is going to be a single left rotation. And then the trees at the

bottom, those are going to be double rotations. Let me just write over here, maybe next to that

one, double right rotation. And then I’ll duplicate this. And this one over here is going to be a

these on different sides than I usually do because I was trying to make it look a little more tricky

but it’s really not that bad. So how do we know that the top pattern is a single right rotation

and not a double right rotation or it’s a single right rotation and not a single left rotation?

The first thing to try to understand is what’s going to happen between the input pattern and

the output pattern. So if you look at the input pattern here we’ve got like a straight line and

And the output pattern is like a perfectly balanced trinode subtree.

Notice how the 55 is the new parent.

And it’s also in the middle for the output pattern.

And then for the input pattern, the 55 is also in the middle, but it’s not the new parent.

But it is the parent already of the 48 node.

Notice how it’s the parent already of one node, the 48 node.

So that means its relationship to the 48 node, the left child, doesn’t actually change.

bit more you’ll realize that only one node actually needs to be moved into position so we’ll call this

a rotation try to imagine visualize maybe like your point your left pointer finger being placed

on the 55 node and your right pointer finger being placed on the 65 node and then just rotate

the 65 node downward we rotate that clockwise and the physics people out there love to say that

are right rotations.

At least as far as I remember.

Not totally sure about that,

but I’m just going to say it anyway.

So notice how the 65 needs to be rotated

to the right or clockwise.

And only one node actually needs to be rotated

to produce that final output pattern.

That’s why we call this a single right rotation

because there’s only one node to rotate.

The next thing I’ll do is just try to give you

a few extra ways of being able to remember

being able to remember whether it’s a left or a right so for starters one node needs to be rotated

so it’s a single rotation and we’re rotating clockwise so it’s a right rotation but you can

also do this you can think of it like can i get rid of that real fast you can think of it like

well there is a bunch of empty space kind of sitting here on the right side so that could be

another way to remember that this is a right rotation also if you were to start at the node

and work your way to the node at the top,

you know, the Z node,

then we’re kind of going up and to the right.

So that’s another way to remember

that this is a right rotation.

Single, you can remember that also

by just the fact that this is a straight line.

Like notice how the nodes are kind of in a straight line.

They don’t do a zigzag or a bounce.

So single rotations are rotations that look straight at first,

or I guess input patterns that look straight

and only one node actually needs to be rotated.

um right versus left is there’s a pocket of empty space on the right side and you go up and to the

right for the right rotations similarly you can probably already figure out by now that

the left rotation just means well we’re going let’s see we’re going up and to the left to get

to that top node or the only node that has to be rotated is that 48 node and it’s going to be

rotated counterclockwise which is left so again only one node needs to be rotated and we’re going

to be rotated and we’re going to rotate it counterclockwise which is a left rotation so

one node rotated single counterclockwise left or just like a pocket of empty space sitting on the

left side okay so then for the double rotations the first thing you can look at is the idea that

there’s a little bit of a bounce you know there’s like a angle bounce there if you see a bounce or

sick a couple weeks ago then that’s a double rotation another way you can try to remember it

as two nodes need to be moved into position so if I maybe I should copy this to another slide real

fast let me copy this and we’ll do another slide okay so you know which nodes need to be moved into

position let me copy also the output pattern just as a quick reminder if we wanted to make that

If we wanted to make that output pattern, let me put it up here maybe,

then obviously the 55 still has to be in the middle

because it was already in the middle before we rotated.

That means both the 48 and the 65 need to be rotated underneath the 55.

So that means we’re going to do the 65, we’re going to rotate it clockwise underneath the 55.

So I’m going to do like a little circle here, a connector, and then I’ll do like 65 there.

65 there and then after we do that rotation we have to rotate the 48

underneath the 55 so that’s going to be a rotation that is counterclockwise so

I’m going to do this circle that there and then do a 48 notice how when we’re

done doing the rotations we have a valid binary search tree you should always

check your rotated pattern your output pattern to make sure it’s actually in

binary search tree because if it’s not let’s say the numbers are out of order for some reason from

left to right then you have rotated incorrectly and you have to double check yourself so two nodes

need to be rotated into position therefore it’s a double rotation or you see a diagonal input pattern

double rotation how do you remember the difference between left and right well um if you start at the

node in the middle just like we did in the last slides we start at the node in the middle and go

and go to the node at the top, the Z node,

we’re going up and to the right.

And so this is a right rotation.

So it’s a double right rotation.

Another way to remember it is you should probably try to rotate the Z node first.

The node that’s on very top is the 65.

Rotate that first and then call that the direction of the rotation.

So, you know, we rotate the 65 first.

That’s a clockwise.

So that’s why it’s a right rotation.

Then just ignore the direction of the other node that you rotated.

you can also kind of imagine taking the original node if you don’t if you don’t

want to think of like actually rotating let me just kind of erase this real fast

you can kind of imagine that you are you’re sort of taking the new parent

that’s supposed to be the new parent and just sort of pulling it up

I draw a picture of Batman and he shoots a batarang at it and he sounds like Christian

Bale and he’s like, where is the rotation?

I’m not going to do that.

Maybe if there are enough comments, I’ll do a special video just for my really, really

bad drawing.

But imagine the 55 is getting pulled up and it’s getting pulled up past two other nodes.

So that’s why it’s a double rotation.

Another way to remember.

The 55 would be the mob boss that’s hanging by his ankle.

anyway so uh we we kind of know how we can remember the difference between uh single and

double rotations uh we’ve got a single right rotation a single left a double right a double

left there’s only going to be four possible input patterns and they’re all going to look like this

one output pattern because really what we’re doing is we’re just we’re not you know creating

any nodes or removing any nodes we’re just disconnecting pointers we’re disconnecting

just get this over here we’re saying okay input pattern I disconnect the pointers I’m saying the

65 no longer has a left child the 48 no longer has a parent the 55 no longer has a parent and

the 48 no longer has a right child and then when we’re done with that we just kind of like reconnect

the relationships we’re like okay you know what just kidding you all have parents and children

again we’re just rearranging them okay let me check out my thing real fast here

I’m going to cut the video here because this is the basic idea for the different types of rotations that you could use.

In the next videos, we’re going to actually start rotating bad trees to make them work.

So thanks for watching this video.

I hope you learned a little bit of stuff and had a little bit of fun.

I’ll see you in the next video.

Okay.

Hey, everybody.

Thanks for watching this video again from the bottom of my heart.

I really appreciate it.

it. I do hope you did learn something and have some fun. If you could do me a please, a small

little favor, could you please subscribe and follow this channel or these videos or whatever

it is you do on the current social media website that you’re looking at right now. It would really

mean the world to me and it’ll help make more videos and grow this community. So we’ll be able

to do more videos, longer videos, better videos, or just I’ll be able to keep making videos in

and subscribe. You know sometimes I’m sleeping in the middle of the night and

I just wake up because I know somebody subscribed or followed. It just wakes me

up and I get filled with joy. That’s exactly what happens every single time.

So you could do it as a nice favor to me or you could you could troll me if you

want to just wake me up in the middle of the night just subscribe and then I’ll

just wake up. I promise that’s what will happen. Also if you look at the middle of

the screen right now you should see a QR code which you can scan in order to go

to the website which I think is also named somewhere at the bottom of this

is also named somewhere at the bottom of this video and it’ll take you to my main website where

you can just kind of like see all the videos i published and the services and tutorials and

things that i offer and all that good stuff and uh if you have a suggestion for uh uh clarifications

or errata or just future videos that you want to see please leave a comment or if you just want to

say hey what’s up what’s going on you know just send me a comment whatever i also wake up for

the night I get I wake up in a cold sweat I’m like it would really it really mean the world to

me I would really appreciate it so again thank you so much for watching this video and um enjoy

the cool music as as I fade into the darkness which is coming for us all

Thank you.

Hello there.

Let’s talk about rotation types in an AVL self-balancing binary search tree.

The post AVL Tree Rotation Types Explained for Self-Balancing Binary Search Trees appeared first on NeuralLantern.com.

AVL Tree Tutorial: Balance Factors and Why They Fix Slow BSTs

mike — Mon, 18 May 2026 06:09:32 +0000

Learn AVL trees in this beginner-friendly introduction. We cover balance factors, why regular BSTs get slow, and how AVL trees stay balanced with rotations. Great for coding interviews and data structure understanding.

00:00 AVL Trees Introduction
00:00:28 Problems with Regular BSTs
00:00:56 AVL Tree Balance Rule
00:02:10 Balance Factor Explained
00:02:48 Computing Balance Factors
00:03:11 Example Tree Analysis
00:04:40 Imbalance at 65 Node
00:05:08 Invalid AVL Tree
00:06:18 Linear Tree Problem
00:06:50 Trinode Subtree
00:07:40 Selecting Z Y X Nodes
00:09:20 Rotation Overview
00:10:03 Next Videos Preview
00:11:09 Thank You and Subscribe

=-=-=-=-=-=-=-=-=

Thanks for watching!

Find us on other social media here:

https://www.NeuralLantern.com/social
Twitter / X: https://x.com/NeuralLantern
Rumble: https://rumble.com/c/c-3696939
BitChute: https://www.bitchute.com/channel/pg1Pvv5dN4Gt
Daily Motion: https://www.dailymotion.com/neurallantern
Minds: https://www.minds.com/neurallantern/
Odysee: https://odysee.com/@NeuralLantern:5

Please show your support!

Buy me a coffee: https://ko-fi.com/neurallantern
Subscribe + Sharing on Social Media
Leave a comment or suggestion
Subscribe to the Blog: https://www.NeuralLantern.com
Watch the main “pinned” video of this channel for offers and extras

Hello there. Let’s talk about a type of self-balancing binary search tree called an AVL tree.

Okay, so by now I hope you’ve seen my other videos that I’ve posted

previously where we talked about binary search trees, how to define them,

terminology, how to know you’re actually looking at one, how to build them, insert,

If you finish those videos already with me, then you know that binary search trees can actually get slow sometimes because if we have bad data, regular binary search trees don’t really know how to rearrange themselves.

They just might become slow depending on how good or bad the data is.

The data is totally random.

Then on average, it’ll, you know, the trees will be log time, but that’s not always the case.

Maybe sometimes you have bad data, sorted data, poison data, whatever kind of data.

The secret to AVL trees is we’re going to start with the binary search tree.

And so first it has to satisfy all the rules of the binary search tree.

And then we add on another rule.

The rule is going to be that we don’t have a valid AVL tree.

If the balance factor for any of the nodes, we’ll talk about balance factors in a second.

If the balance factor for any node is two or worse.

Meaning if we think the tree is too imbalanced at any node, it’s not a valid AVL tree.

and therefore we must rebalance the tree with something called a rotation.

After we do enough rotations and we see that the tree is balanced again, then it’ll be valid.

And so AVL trees sometimes are invalid in some intermediate state.

Like if you have an AVL tree and you add some data into it,

for a moment it might be an invalid AVL tree and then internally it’s sort of just like rotating itself and rebalancing itself.

Then when the tree is done, you’ll have a valid AVL tree again, if that makes sense.

AVL tree again if that makes sense. So suppose this tree here we can tell this is a valid binary

search tree because it follows all the rules that we talked about before. So let’s start implementing

the first rule of an AVL tree which is let’s compute the balance factors for every single node.

How do we compute balance factors? The basic idea is I want to say BF for balance factor

the left subtree height minus the right subtree height.

If you don’t know what a subtree or height is,

you should probably check out my other videos right now.

But basically, we’re just going to take the absolute value

just to get the difference in the height of the left

and the height of the right.

So if you know binary search trees already,

then you know that the leaves, they don’t have any subtrees.

So their balance factor is going to be pretty easy to compute.

It’s just going to be a zero.

I should also point out that some other tutorials out there use positive and negative numbers

for the balance factor.

That’s okay.

I’m just going to use absolute values here because it’s a little bit more simple.

So all the leaves get a balance factor of zero, which is fine.

We’re looking to see if we can find a balance factor of two or worse to indicate to us that

we have an invalid AVL tree.

So far, so good.

Let’s look at the 22 node.

we’ll compute the height of the left subtree versus the height of the right subtree.

So, you know, I’m going to highlight its left subtree.

That’s just the 14 node that has a height of 1.

And then its right subtree is just the 36 node that also has a height of 1,

which means the balance factor for the 22 node is the absolute value of 1 minus 1 is 0.

So actually the 22 node is perfectly balanced.

If you think about it, that makes sense.

Left and right subtrees have the same height.

No problem.

have the same height no problem so I’m going to move on let’s compute the balance factor for the

48 node this is a little trickier notice how the right subtree has a height of one and there is no

left subtree which means its height is zero so for the 48 node it’s actually going to be

the absolute value of zero minus one or just one so we find our first node that’s a little bit out

imbalance here but avl trees tolerate imbalances of one they don’t really care we sort of try to

make a trade-off between constantly always rotating every single time anything happens

which would perhaps burn a little too much cpu versus letting the tree just be imbalanced to a

reasonable amount so we could still call this a log tree in the end so we consider this to be okay

65 node and compute the balance factor so 65 node has no right subtree so the height is zero there

and its left subtree is those two nodes on the left so that has a height of two which means the

balance factor for the 65 node is going to be the absolute value of two minus zero is two at this

point we are already certain that this is not a valid avl tree and it would need to be rebalanced

you know, consider it a valid AVL tree in the future.

So invalid AVL tree, still a valid binary search tree.

Something has to be done.

Normally what I would say is if you find some nodes

way down lower in the tree that are imbalanced,

then just go ahead and perform a rebalancing

or a rotation immediately,

because sometimes when you rotate lower in the tree,

you’ll end up fixing nodes that are a little higher.

But since we started with this tree

and we’re not kind of, you know,

building a tree step-by-step,

I just want to compute the balance factor for all of the nodes at the same time.

So we’ll do the same thing for the 41 node, the root node.

Its left subtree has a height of two and its right subtree has a height of three.

So its balance factor is the absolute value of two minus three is one.

So actually the root node is okay.

If it was only up to the root node, we would say this is a valid AVL tree

and we don’t really need to do anything.

need to do anything however we’ve already seen that the 65 node is invalid so again uh we we

need to do something here’s another quick example before we move on to actually identifying which

nodes to to modify and rotate just real fast i want to show you you know that a binary search

tree could actually end up being a linear tree if you had really really really bad data the binary

This is slow because this is a linear tree.

The time complexity of searching through this tree is linear time.

It scales linearly with the number of nodes in your data set.

That’s really far away from log time, which is supposed to be lightning fast.

So an AVL tree will fix this kind of bad data.

Let’s take a step back here and focus your attention for a second on these three nodes.

We noticed that there is one node that’s actually out of whack.

It’s the 65 node, right?

What we’re going to do is we’re going to find a trinode subtree that starts with the first node or the lowest node we can find that’s out of whack.

It’s the 65 node.

And you can tell that if we just kind of go down a level and down another level to select the other two nodes,

it’s just going to be this little, you know, subtree of three nodes or otherwise known as a trinode subtree.

So here’s kind of a diagram for that.

Whoops, forgot to delete that earlier.

Let me get rid of that.

So this is the trinode subtree that we selected, right?

So we’ve got the 65 and the 48 and the 55.

How did we actually select this?

So what you kind of want to do is the first node that is out of whack,

you want to call that Z.

So I’m going to write a Z here.

What we’re looking for is a trinode subtree,

which we’ll first call X and Y and Z.

And then we’ll end up reordering the nodes

and then rearranging all the pointers to the nodes

so that the trinode subtree is a little bit more in balance.

more in balance. So we see the Z node. We have to find the Y node next. To find the Y node,

what’s going on with my computer? Oh, there we go. We have the Z node. To find the Y node,

really, we’re just going to take the child of the 65 node that has the taller subtree. So

there’s only one subtree, you know, on the left, there’s no subtree on the right of the 65 node.

So the choice is obvious. But just so you know, if there was, you know, another, you know, child

another you know child hanging off of the right for some reason we would still choose the number

48 node as the y node because it has the taller subtree notice how the subtree on the left is two

and the subtree on the right has a height of one so always take the taller subtree when you’re

looking for uh y and then x so then we do the same thing we go down to the grandchild of the z node

and if we had a choice to go left or right again we would always choose the taller subtree in this

taller subtree in this case there’s only one choice so that x node is going to be the 55

now in this next slide i’ve kind of redrawn this in a little bit different of a way

notice the trinode subtree that we just selected here the 65 48 55 subtree it has a height of three

i mean that should be obvious right it’s just got a height of three

or height. Notice on the left, these are the same three nodes. Exactly. 48, 55, and 65. That’s the

same three nodes that we originally had. But notice how the height is too. So the basic idea for ABL

trees is, you know, compute the balance factors. And as soon as you identify a node that’s out of

whack, you grab a tri-node sub-tree starting at the node that’s out of whack, the Z node.

And then we’ll perform, quote unquote, a rotation where we just kind of smoosh it to be a little

be a little bit more balanced and a little bit more a little bit shorter so the height goes from

three to two once we do that the rest of the tree it’s going to get a little bit better you’ll notice

that this will end up sometimes completely but sometimes partially fixing bad balance factors

in the tree so um this is the end of the intro i only wanted to spend a little time just kind of

like warming you up to the idea in the next videos uh we’re going to actually look at performing

identifying the four different types of rotations that you could see and like how to do them.

We’ll talk more about the idea that we’re really just rearranging pointers here.

If you’re thinking about code, you’re thinking about, oh, I’ve got some pointers between these

nodes. We’re not going to delete any nodes or add any nodes. We’re just going to like

rearrange who is a parent of who, who is a child of who. And then eventually we’ll deal with some

really bad trees and we’ll become experts at just like maintaining ABL trees.

talk about ways to visualize the rotations, which makes it a little bit easier to remember these

patterns and stuff. Okay, so thank you for watching this video. I hope you learned a little bit of

stuff and had a little bit of fun. In the next one, we’re going to get started. We’re going to

go deep. I’m going to get my gear. Sorry.

Hey, everybody. Thanks for watching this video again from the bottom of my heart. I really

from the bottom of my heart. I really appreciate it. I do hope you did learn something and have

some fun. If you could do me a please, a small little favor, could you please subscribe and

follow this channel or these videos or whatever it is you do on the current social media website

that you’re looking at right now? It would really mean the world to me and it’ll help make more

videos and grow this community. So we’ll be able to do more videos, longer videos, better videos,

Do me a kindness and subscribe.

You know, sometimes I’m sleeping in the middle of the night and I just wake up because I know somebody subscribed or followed.

It just wakes me up and I get filled with joy.

That’s exactly what happens every single time.

So you could do it as a nice favor to me or you could troll me if you want to just wake me up in the middle of the night.

Just subscribe and then I’ll just wake up.

I promise that’s what will happen.

Also, if you look at the middle of the screen right now, you should see a QR code which you can scan in order to go to the website.

in order to go to the website which i think is also named somewhere at the bottom of this video

and it’ll take you to my main website where you can just kind of like see all the videos i published

and the services and tutorials and things that i offer and all that good stuff and uh

if you have a suggestion for uh uh clarifications or errata or just future videos that you want to

see please leave a comment or if you just want to say hey what’s up what’s going on you know

I also wake up for those in the middle of the night. I get I wake up in a cold sweat and I’m like

it would really it really mean the world to me. I would really appreciate it. So again thank you

so much for watching this video and enjoy the cool music as I fade into the darkness

which is coming for us all.

Thank you.

The post AVL Tree Tutorial: Balance Factors and Why They Fix Slow BSTs appeared first on NeuralLantern.com.