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
arkro: 2014-09-20 06:52:50

Got a lot of WA for writing "yes" and "no". Finally AC! :P

Dhruv Raj Singh Rathore: 2014-09-05 11:05:13

what if graph is disjoint and separately both of them form a tree
6 4
1 2
1 3
4 5
4 6

Brij Vaid: 2014-08-24 20:32:36

how to solve without dfs?

do_do: 2014-08-22 08:07:26

union-find algorithm worked... :)

anand pandey: 2014-08-16 01:59:11

Last edit: 2014-08-16 14:30:58
anand pandey: 2014-08-16 01:58:44

[code removed by cyclops; see notes below, "1. Don't post any source code here."]

Last edit: 2014-08-16 04:21:23
Naruto uzumaki: 2014-08-15 18:39:13

@jarvis this is a tree,

Miroslav Kovar: 2014-08-12 20:40:11

Please, what are some tricky test cases? I am getting WA, although the algorithm works fine for everything I come up with...

.:: Jarv1s ::.: 2014-08-10 00:50:28

4 3
1 2
2 3
2 4

is giving YES for AC solution, is it correct? Admin please rejudge all solutions...

mohsin mohammad: 2014-08-06 16:37:56

My first graph problem AC in first attempt
really exciting........