Lecture 88: Cycle Detection in Undirected Graphs || Using BFS and DFS

[@gargkapil]

this entire series is much much much better then so many paid courses.

[@muzammilaltafmulla]

You forgot 'very very' before those 'much'...

[@thinkverse94]

Thanks, Babbar bro for the superb explanation and your enthu :) Here just I wanna add a point, that is much easier to understand to detect loop:- // if the number of visited nodes in any adjacency list is >=2 then there is a cycle. // no need for extra parent data structure Sample code which passed all the test cases:- bool isCyclicBFS(int node, unordered_map &visited, unordered_map &adjList) { queue q; q.push(node); visited[node] = true; while(!q.empty()) { node = q.front(); // counter for already visited nodes int cnt = 0; //traversing the adjacency list for(int i: adjList[node]) { if(!visited[i]) { q.push(i); visited[i] = true; } else { cnt++; } } q.pop(the ); // if the number of visited nodes in any adjacency list is >=2 then there is a cycle. if(cnt >= 2) return true; } return false; }

[@samsmith3961]

how does it work i am not able to comprehend the concept used here , wont count be considered 0 everytime the loop makes another iteration

[@thinkverse94]

​@@samsmith3961 very simple, if the number visited adjacent nodes >=2 for a node ... that means one is a parent and at least one node will be there which is visited but not a parent ... that's how you co-relate

[@thinkverse94]

@@samsmith3961 see the count is initialised 0 before calculating the adjacent nodes for a node, it will continue to count until all the adjacent are covered for a particular node, that's how we can track the number of visited adjacent nodes, and at the end we checking is it >= 2 or not

[@hinalvakharia2744]

will it work for DFS?

[@KushalSharma-d3q]

​@@hinalvakharia2744if adj list has >=2 elements with visited==true that simply means it has a loop so its a condition for a loop whatever approach u go with

[@shalinisaini3787]

Thankyou Bhaiya for this amazing course

[@barnikroy5244]

at least you kept your word to complete this course .........salute once more

[@samsmith3961]

yeh course kaafi underrated hai... i hope people would soon pay attention to a treasure trove of a channel like yours!!!! kudos to you and pls keep up the good work.

[@hameedmulani21]

Its very good course with Complete Dry Run of Example that is what I want

[@vaibhavrathod9674]

Finally I have watched this video 3 times, now I properly understand how this works.. Thank you so much Bhaiya...... Love you from Gujarat💖💖

[@ShouryaPant]

Finaaly Our Beloved Babbar Bhaiyya Is Back Bass Ab Consistency Bhi Apnr Babaar Bhaiyya Ki phle jaise vapis Aajye Maza Aajayega🙂🙂🤩🤩

[@AdityaRaj05]

Sir provide complete notes 15-16 and from 41 to above also Ur notes is too good sir . Plz provide us so tat we can revise easily.

[@crazykidda5831]

very nice lecture....I can't believe I could have understand all these when I started. But u are too good.

[@darshanpatel9131]

bool isCyclicDFS(int node,int parent,unordered_map &visited,unordered_map &adj) Here why are we passing the adj list with pass by reference method ? Since there is no relation with the changing the values present in the adj list.

[@muhammadsuleman8936]

Lecture was super amazing i recomment this playlist to everyone>> Amazing content zbr10

[@vmstudy9965]

Bhaiya mjaa aa gya. Aisi dry run krk btaya kro 🎉❤. Ekdm chumeshwar tha 😅

[@prashantbirajdar9271]

bhut achaa ++ hai bhiya subkuch samaj ayaa nice bhaiya thanks..love u bhaiyaa....

[@alexrcrew1975]

-- --

[@abhijeetbasfore6816]

bhaiya BFS algo use jab apne kara parent ke liye different ds nhi banake queue ho jata na

[@beinghappy9223]

Thank u bhaiya Best video on Cycle Detection available on KZbin ❤

[@shubhammalhotra7244]

For every visited vertex v, if there is an adjacent u. Such that u is already visited & u is not the parent of v. So, cycle in the graph is present/

[@nishankdeep3084]

thank you bhiaiya saare concept ache se clear hue bhaiya concept learn++

[@ShivamGupta-qn7lj]

We can also use vector adj, but it shows runtime error 16:25

[@ankitchavhan]

Well explained!! Just one feedback... Please highlight your mouse pointer with some color.

[@jhordd52]

bhaiyaa plzz video length badhado and good to see you back again just questions krvado bhaiya jese pehle topics mai krvaye hai baaki sab op hai aapke hmare liye itne efforts bhi kam nhi hai

[@RohitSingh-hc8yi]

loving this course bhaiya

[@harshpandey4190]

Lecture is Amazing ++

[@vishalgarna4580]

Samajh aaya gaya bhaiya

[@rachit_joshi]

Thank You So Much BHRATA SHREE !!!!!!!

[@apoorvaron46]

for next time, Please do dry run with small examples

[@syedmuhammadabdullah2920]

Thankyou so much for successfully wasting my time

[@mancunianswagger3668]

Finally video aayi ek❤ Daalo bhaiya daal do saari do mahine me placements hain krwaado tayaari fir mail me thankyou jarur bhejenge promise 🤞😅

[@salmankhader1258]

plz discuss time and space complexity as well

[@amitnagdev7061]

In Simple Words, agar koi ek node k do 'mai-bap' mile toh samaj jana k voh ek cyclic component hai uss graph ka.😄

[@barkhagupta5237]

😂😂😂😂I willl remember this logic @amitnagdev7061

[@tayyab.sheikh]

Point!

[@mr.writer2903]

Now, i am realize just see whole logic and write code by yourself. it's possible that you find better code 🙃.

[@slowDrive4]

you can just use an extra set instead of object or dict

[@vanshgoyal1356]

Actually I've a doubt !! Here "src" is basically "i" and we are doing "q.push(src)" so are we considering that the graph will always contains a 0 as a vertex and will always run from 0 to V. Please correct me if I'm wrong. Thank you ❤❤

[@sanipatel1272]

Yes bro we are starting vertex from 0 to its value.

[@anuragpandey8165]

Boht achaa lecture........... par consistency chahiye babbar bhai

[@GauravHaritas]

bhaiya k editor ko bhi DSA aa gya gaya hoga ab tk to itni videos dekh dekh k

[@utkarshsingh1457]

Thanks for the video bhaiya... ❤️🔥

[@bite091_jamee7]

amazing bhaiya

[@iamvishnuranjan]

Bhaiya plz end this course before placement 😭😭😭

[@VivekSingh-xg5mn]

best videos on DSA and algo for sure on internet

[@AmanKumar-io3ev]

but bhaiya what will happen if nodes are not 1,2,3 despite of a ,b ,c

[@subratamandal2924]

Yes in that case indexing will be a problem. You can do arr['a'-char] to store

[@haiderali0801]

amazing bhaiya......

[@heighlights012]

bhai code kaha pe milega ye vala mera problem de raha code link mai sirf lec 44 tak hi hai

[@Learnprogramming-q7f]

Thank you Bhaiya

[@PrakharSaini-zw8nz]

Thanx for this video and your unbeatable efforts..

[@sounaksaha1455]

maza aa gaya bhaiya

[@SatyamKumar-x6m1l]

sir eska code kaha hai jo link hai usma bass tree tk ka hi code haii graph aur bakki lecture ka code ka link kaha hai

[@MrKalwar]

bahut badhiya bhaiya!!

[@footballcreativeeverywhere260]

Jai hind ❤️🇮🇳

[@adityavishwakarrma514]

Ho jayega course complete complete++

[@IndianGao]

are you fine bhaiya ji please notes bhi send kar dijiye 14-15 and 41 se aage ka

[@apoorvyadav3378]

Bhaiya is back 🔥🔥🔥

[@shivkumar-og4ow]

thank you bhaiya .. for your hard work . Doing a good job

[@KCOYASH]

completed and thanks for the video

[@SFAbhi9642]

@Love Babbar bhaiya which keyboard do use for programming

[@piyushkumar-wg8cv]

For better experience, watch in 1.25x speed. Meanwhile me who was already watching the video in 1.5x :- 🌝

[@yutubegaming5340]

1.75

[@alokranjan3185]

Thanks bhaiya ,wait is over

[@ks-xh4fq]

Why parent of neighbour = front ? Line 24

[@saujanyashukla5483]

Good to see u back bhaiya keep the consistency up again ❤️

[@itzheavem4451]

last community post added last week he said we will be consistent now abhi es video mei bola hai ki 13 tarik k baad se consistent ho jayenge toh hisab sidha sa hai ab pehle wali baat nhi reh gyi hai course mei videos ki length v choti kr di gyi hai jabki feedback v diya tha last video mei. or padhane k style se pta lag rha hai wo pehle wale enthusiasm se nhi padhaya ja raha hai

[@saujanyashukla5483]

@@itzheavem4451 u are right bro

[@grandson_f_phixis9480]

Thank you very much sir

[@vishalgarna4580]

Acha nahi bahut accha 😊😊

[@Deepak-um1zq]

nice lectures❤

[@tejasshaha6629]

We trust you bhaiya ❤

[@prashantaarya3852]

awesome explanation

[@akankshapandey9773]

Thanku so much sir , sir pls series complete kr dijiye 2 month me placement hai pls sir 🙏

[@jimarrafi5881]

Bhai, Please make video on String Matching. It will be really helpful to us.

[@amishapandey6875]

Well explained!

[@KratosProton]

great explaination

[@iteself_me]

133 ✅completed 👍Liked 5:3

[@ayushgupta1881]

Thanks a lot bhaiya

[@abhinavtiwari6405]

Bohot acha lga ❤️

[@fazerugbrug439]

superb

[@diyatoliya9067]

Loved it!!

[@govindnair3135]

thamks a lot bhaiyya

[@B-NikhilRichhariya]

bhot achhaa

[@cse_29_abdulshariqkalim15]

Bro please make videos regularly

[@yashasvic2429]

Thank You bhai 👍

[@adamyasharma_0135]

best!

[@chandrasubhashinithakran8323]

// code for this lecture #include #include #include bool iscyclicBFS(int src, unordered_map &visited, unordered_map adj){ unordered_map parent; parent[src]=-1; visited[src]=1; queue q; q.push(src); while(!q.empty()){ int front = q.front(); q.pop(); for(auto neighbour: adj[front]){ if(visited[neighbour]==true && neighbour!=parent[front]){ return true; } else if(!visited[neighbour]){ q.push(neighbour); visited[neighbour]=1; parent[neighbour]=front; } } } return false; } bool iscyclicDFS(int node,int parent, unordered_map &visited, unordered_map &adj){ visited[node]=true; for(auto neighbour: adj[node]){ if(!visited[neighbour]){ bool cycledetected=iscyclicDFS(neighbour, node,visited,adj); if(cycledetected) return true; } else if(neighbour != parent){ //cycle present return true; } } return false; } string cycleDetection (vector& edges, int n, int m) { // create adjacency list unordered_map adj; for(int i=0;i

[@dEviL_bIsWaJiT]

Best dsa course ever.:) #dsabusted

[@TANYAGOSWAMI-m3g]

thanks bhaiya

[@focus.placement5589]

thanks bhaaiya

[@iamvishnuranjan]

Plz end this course before placement 😔😔😔😔😔

[@S4UR4BH4]

kya baat!

[@shubhamkhare26]

Great video...

[@sheetalmittal6240]

Best DSA course

[@sukhjitsingh959]

We are present Babbar B

[@063himanshumishra4]

Bhaiya moj kr diii

[@mysticmuskan3529]

Thank u sir

[@GuruPrasadShukla]

sahi tha bhaiya thx

[@sarthakjain1824]

Much easier approach with lesser space complexity class Solution { public: bool bfs(int i,vector adj[],unordered_map &visited){ queue q; q.push(i); while(!q.empty()) { int temp=q.front(); visited[temp]=true; if(q.size()>1) { if(q.front()==q.back()) return true; } q.pop(); for(auto j: adj[temp]) { if(!visited[j]){ q.push(j);} } } return false; } bool isCycle(int V, vector adj[]) { unordered_map visited; for(int i=0;i

[@voicechanger3635]

TLE mar rha hai ye code to

[@KhushiKavya-py1yj]

i was not consistent but i will try to be now

[@nikhilsingla4107]

best course in DSA

[@collegebkchodi6687]

Bhaiya problem practice krao graph ka

[@vedantdeshmukh4949]

Bhaiya ab quality++ aur consistency++ krlo bs 🥹

[@itzheavem4451]

agle ne bol toh diya firse 13 tarikh k baad se consistent ho jayege. wese he jese har video mei bola jata h lekin 2 mahine se consistency ka koi tikhana nhi h

[@raghavattri9449]

Bhaiya new course ki announcement kab hogi😅

[@chintaphaniramavaibhav3714]

babar bhai please provide us with notes and code bhaiyya

[@shresthkaushik6636]

🙏🙏🙏

[@amantarar9077]

Bhaiya course kab khtm hoga ? Date btado

[@arpit7618]

awesome

[@mohdshaban2824]

LOVE