SPOJ.com - Problem PT07Y

PT07Y - Is it a tree

#dfs

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

Input

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).

Output

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

Example

Input:
3 2
1 2
2 3

Output:
YES

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	Mihir Saxena: 2016-05-19 19:24:16 Getting sigsegv error, what can be the possibility? Tried another approach, didn't create an array, instead used the union find algorithm directly on the edges and then in the end, checked the condition of connected graph, still got a WA Last edit: 2016-05-19 20:02:58
	Luis Herrera: 2016-05-13 22:20:50 Interesting problem. Hints: A graph is a tree if: - It has no cycles - It is connected
	anupamwadhwa: 2016-05-12 20:38:21 if any node is not connected to rest of nodes then it should YES or NO
	dinkar: 2016-05-01 10:23:14 Nice problem, got to learn about union find.
	lisbecg: 2016-04-15 03:22:32 Did you guys build the graph in order to do DFS?
	sharif ullah: 2016-03-12 12:31:25 just use union find check if there is a loop!
	vimal: 2016-03-06 17:12:11 accepted on codechef... WA here... :D UPDATE : solved. hint:what are 3 important prop. of a tree ? Last edit: 2016-03-06 17:24:21
	Neeraj Singh Aithani: 2016-02-16 16:56:15 Actually Test Cases are very weak my solution for 4 3 4 2 4 3 2 1 is NO.But it is AC
	dkumarsingh: 2016-01-22 21:14:52 i am using matrix to represent it's structure as a graph but getting sigsev error
	Aqib Ahmed J: 2016-01-16 06:00:11 Tree doesn't have loops ! Cost me one WA :\|

Submit solution!

Added by:	Thanh-Vy Hua
Date:	2007-03-28
Time limit:	0.5s
Source limit:	50000B
Memory limit:	1536MB
Cluster:	Cube (Intel G860)
Languages:	All except: ERL JS-RHINO
Resource:	Co-author Amber