Sphere Online Judge

SPOJ Problem Set (classical)

1436. Is it a tree

Problem code: PT07Y


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

Added by:Thanh-Vy Hua
Date:2007-03-28
Time limit:1s
Source limit:50000B
Memory limit:256MB
Cluster: Pyramid (Intel Pentium III 733 MHz)
Languages:All except: ERL JS
Resource:Co-author Amber

hide comments
2013-01-11 09:42:15 Aayush


Last edit: 2013-01-11 09:56:51
2012-11-21 03:31:53 Paul Draper
Weak test cases. Trees are always built in order; i.e. no
4 3
1 2
3 4
1 3
2012-11-14 19:51:05 kailash
Can I get some test cases.
My code is working for my inputs but spoj is showing WA.
2012-09-19 22:15:01 Ashwin Menon
Are the nodes contiguous?

1, 2, 3 ... N?
2013-12-30 05:22:25 KEVALSAHU
simple problem guys :)

Last edit: 2012-08-26 01:14:34
2012-06-21 09:40:19 +2 RIFAI


Last edit: 2014-02-27 08:09:25
2012-05-01 18:51:58 Diego Guapo Mendieta
give me the solution :D
2011-11-04 06:11:52 tracy filbert ridwan
just a simple flood fill :D
2011-07-22 17:55:06 pavan
weak test cases
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