PT07Y - Is it a tree

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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:0.166s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel Pentium G860 3GHz)
Languages:All except: ERL JS SCM chicken
Resource:Co-author Amber

hide comments
Rahul Jain: 2015-01-25 01:19:39

@krishan kumar, the ans should also be NO

Ankur Mohanty: 2015-01-22 13:13:25

recommended for graph beginners

Kishlay Raj: 2015-01-11 19:09:03

easy stl set ;)

Last edit: 2015-01-11 19:09:17
Nick Jiang: 2015-01-08 10:07:07

Last edit: 2015-01-08 23:26:48
Anubhav Gupta: 2014-12-28 19:30:24

simple DFS :)

agaurav77: 2014-12-09 18:51:22

A basic implementation of union find algorithm works, so agreed, hussein. AC!

Shivam Mitra: 2014-12-04 12:59:44

BFS using adjacency matrix: 0.16s,385M
BFS using adjacency list: 0.00s,3M
:p

hussein: 2014-11-08 15:05:16

A simple loop with parents array is enough .. no need for DFS or BFS or any graph traversal algo