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
2014-07-09 11:45:30 Shireen Nagdive
Can anyone give hints how to solve the code without dfs and bfs?
2014-07-05 16:20:30 chin
getting seg fault..:(
Finally got AC..:D..got my mistake..

Last edit: 2014-07-07 04:56:16
2014-06-11 10:14:08 Manu Narsaria
Submission ID:11738679
Please check it satisfies all possble input that i could find....
2014-05-26 06:40:47 dragonemperor
Weak test case. In none of the cases, number of edges is less than number of vertices. I have a condition that checks if number of edges is less than number of vertices minus 1. If it satisfies, my code is not taking edges as input but I still got AC.
2014-05-20 22:09:10 Suraj Rajan
cycles and connectedness..!! :)
2014-04-23 20:18:04 Sudarshan K
My very first DFS problem. :)
2014-04-11 18:37:26 sehwag
easyone...

Last edit: 2014-04-11 18:40:52
2014-04-11 13:03:18 ITSMYLIFE
gud1 nd easy1 simple dfs
2014-03-29 21:25:37 Anubhav Balodhi
Easier than I thought... agreed with both the points of @Rastogi..
2014-03-17 11:59:31 Anuj Yadav
No need for BFS or DFS !! easy one .
© Spoj.com. All Rights Reserved. Spoj uses Sphere Engine™ © by Sphere Research Labs.