[7.3] Breadth First Search(BFS) in Python | Graph Theory | Data Structures in Python

In this tutorial we will implement BFS algorithm in Python.
Breadth-first search is an algorithm for traversing or searching tree or graph data structures. It starts at the tree root, and explores all of the neighbor nodes at the present level before moving on to the nodes at the next level.
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#graphtheory #bfs #python #datastructures #algorithms

[@ThinkXAcademy]

Use this dictionary:
graph = {0: [1, 2], 1: [2,3,0], 2: [3,1,0], 3: [1, 2]}

[@shabareesharyan]

Hey, i just wanted to clarify one thing that is use a list instead of set. Because set treats each element as a unique object instead of a sequence. I tried sets and it prints the visited nodes in random fashion everytime. Using list solves that problem

[@amanlall8496]

In your graph, 2nd vertex should be
2:[0,1,4]
and not
2:[0,1]
but it worked anyway

[@ivoperes674]

Thank you very much, I've watched many BFS tutorial videos and this is the best I've seen. Your explanations are clear and precise and your scripting is easy to follow along with.

[@ThinkXAcademy]

Thanks😀This really motivates me to create these videos😄

[@mister_bake2743]

Thanks, simple and understandable explanation!

[@ml9421]

It is so well explained please make a video on dFS, DLS, uniform cost search, and greedy best-first search implementation in python

[@ernesto_quintana]

Thank you !!!

[@ibnefayaz5107]

Thanks ❣❣

[@prachidhawane2984]

Thanks

[@MohitSharma-xf9wp]

Thanks bro, much helpful !!!

[@ThinkXAcademy]

Thanks bro😄Share my videos to help my channel grow💯

[@056_anmolkumarojha2]

good explanation loved it !!

[@ThinkXAcademy]

Thanks☺️Make sure to share our videos to help this channel growth💯

[@shellysinha5429]

Write a function called searchBFS which given the tree or graph as defined below returns every number smaller than 4 in the order it was found using the breadth first technique.

[@ThinkXAcademy]

can you show graph of this question?

[@shivangishahi1268]

Nice explanation!

[@ThinkXAcademy]

Thank you🙂 Share our content to support👍🏻

[@Abhishekkumar-jl2dr]

Thank you so much for this video.

[@ThinkXAcademy]

Please share our videos to help this channel grow😊

[@Abhishekkumar-jl2dr]

@@ThinkXAcademy please give me some ideas or approach to solve this question
"Knight and Bishop meeting point on a 8*8 chess board and few blocks are blocked" Please give me some ideas

[@kashifsohail9188]

thnaqu so much man

[@ThinkXAcademy]

Please share my videos with other students to help this channel grow🌟🧑🏻‍💻

[@aneeshgarray5569]

set function cannot be taken as it sorts the data in it.
try it by changing the root node.

[@ThinkXAcademy]

in visited array order does not matter even if it sorted the algorithm will work.
Change graph dictionary to this and it will work with any root node:
graph = {0: [1, 2], 1: [2,3,0], 2: [3,1,0], 3: [1, 2]}

[@aneeshgarray5569]

@@ThinkXAcademy u r printing the visited array as final result
So order matters

[@ThinkXAcademy]

i ran the program and the result i am getting is not sorted, tried with node 2: output was 2,3,1,0 which is not sorted

[@akanshgoswami4899]

@@ThinkXAcademy i am getting the sort output, tried with node 2 : output was {0, 1, 2, 3}.

[@sakethdamam3280]

@@ThinkXAcademy when we run set() returns new output everytime

[@sahinmuratogur7556]

in your graph dictionary 2 has a connection with 0,1 and 4. In the grap dictionary,which you defined, "2" has only two connections 1 and 0, should that list include 4 also?

[@ThinkXAcademy]

you can add 4 in that list but i have added node 2 in the list of nodes of 4 so that's fine but do not add it in both that will give unexpected output

[@titasarirahmawati1587]

@@ThinkXAcademy so in dictionary 1 only connected with 2

[@titasarirahmawati1587]

1:0,2.. must 1:2

[@ThinkXAcademy]

in the dictionary you can see 1:[0,2]
so 1 is connected with 0 and 2.

[@makaranddeshpande2621]

what is the link for video you mentioned about cycles in undirected graph

[@ThinkXAcademy]

Video and Code is available on this website just go to the course and find the video: www.thinkxacademy.com

[@nazarbylen6737]

nice vid but pls explain why we add firstly to queue if we could just add straight to visited array???

[@tusharvyavahare9229]

first element in the queue tells the program, where you are in the graph at the moment, so at first you're at root, hence root should be in the queue at start [if queue is empty, the while loop won't start]. You're adding a node to visited set, when you're going to leave the node for further travelling. Also set in python is unordered(mostly doesn't store elements in the insertion order), so you should not use set.

[@ThinkXAcademy]

Great explanation @Tushar

[@roshaantaha2365]

why did we use visited= set() ? As we are defining a condition which will not repeat the visited nodes

[@SJ-kp2hq]

Nice observation 😅

[@manthole]

How can we upload text file into dictionary

[@056_anmolkumarojha2]

Can you please make a video on recursion how to master it from zero level questions to advance means from basic to advance.. Please can you?

[@ThinkXAcademy]

ua-cam.com/video/0Bb90KyMlpw/v-deo.html

[@ThinkXAcademy]

This will give you good idea about recursion👍🏻

[@056_anmolkumarojha2]

Thank you , also if possible please provide your viewers a path how to master important topics like recursion, trees, graph, greedy DP will be very helpful 😊

[@ThinkXAcademy]

sure i will

[@md_arfin_cse]

Plz complete course bro

[@ThinkXAcademy]

Working on it..

[@black_eye7105]

Yes bro complicate all the topic.

[@md_arfin_cse]

@@black_eye7105 ty bro

[@kaushaldhungel4773]

Waiting for DFS

[@ThinkXAcademy]

Coming tomorrow ✅

[@pravingupta1814]

bro we RE FIND TO SHORTEST PATH FROM INITIAL TO GOAL, so 0,1,2,4 is answer why you are printed 0,1,2,3,4 in this case 3 is not connected to 4 .

[@ThinkXAcademy]

This is breadth first search technique, it does not aim at finding shortest path. It is a graph traversal algorithm which visits every node in the graph

[@siriuseneegy4484]

H'atr hetyet hìerël hâyarŕ nös?!