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PT07Y - Is it a tree

You are given an unweighted, undirected graph. Write a program to check if it's a tree topology.


The first line of the input file contains two integers N and M --- number of nodes and number of edges in the graph (0 < N <= 10000, 0 <= M <= 20000). Next M lines contain M edges of that graph --- Each line contains a pair (u, v) means there is an edge between node u and node v (1 <= u,v <= N).


Print YES if the given graph is a tree, otherwise print NO.


3 2
1 2
2 3


hide comments
peeyush taneja: 2015-06-11 20:12:42

NIce question

mayank: 2015-06-08 23:30:52

They are not checking for edge disconnectivity in graph (ie. already given m=n-1).Good problem though.

Manish Sombansh: 2015-06-05 10:18:35

I am trying to solve this problem using union-find. but am getting TLE. Can anybody please tell me what's the error? My source code :

BRAIN: 2015-06-04 16:26:13

using dfs or bfs to check connect and using FindSet and Union of Kruskal algorithm to check circle

Shubham Khilari: 2015-05-29 17:52:14

my first problem in graphs. solved in O(n^2).Did not use any stl or dfs bfs.Just try to find if there is a cycle or not..and then u r done.Executes in 0.09.Is there a faster way?

I got two WAs for using just use long long int(that was my bad lol )

Aman Agarwal: 2015-05-26 10:42:53

1st question of graph.. :)

anksin: 2015-05-24 18:01:15

Just one graph traversal, no need to apply union find!!!!

pk: 2015-05-23 08:29:50

AC in 2nd go... union find algorithm is easy... just a few few line of code... :)

Rakend Chauhan: 2015-05-22 15:54:41

maintaining a proper visited array is enough to solve this problem

rpc1: 2015-05-19 22:37:29

@Pavan Thangella: You got lucky! There is one instance in this problem so you had a 50% change of getting it right. There is no way around having to do a bfs/dps. You have to search in any case to check the connectivity of the graph. See "" for more info.

Added by:Thanh-Vy Hua
Time limit:0.166s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel Pentium G860 3GHz)
Languages:All except: ERL JS
Resource:Co-author Amber