PT07Y - Is it a tree


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

hide comments
sonam: 2014-02-02 08:25:13

mai DFS use kar rahi hu to wo to O(2*E) me ho jata hai to phir TLE kyo plz tell me.mai bahut dino se try kar rahi hu

sonam: 2014-02-02 08:22:23

i am using adjecency list and use DFS.
still i m getting TLE.can any one tell me why plzzzzzzzzzzz.

Shubham Sharma: 2014-01-21 16:41:12

Very Weak test cases !

adze: 2014-01-10 23:52:01

@Paul Draper
answer for test case
4 3
1 2
3 4
1 3
is YES, no need to build tree in order

Bhavik: 2013-12-10 15:00:16

kindly check my solution id:10630933
giving WA..don't know why?

Avaneesh Rastogi: 2013-11-13 16:31:12

1) The number of nodes should be raised to a million with the same time limit, to reject solutions which apply a sub-optimal approach
2) Weak test cases should be fixed as reported by other coders.

blc: 2013-11-05 18:43:58

What are the expected answers for the following graphs?
1 1
1 1

2 2
1 2
1 2

Last edit: 2013-11-05 19:18:10
Legolas: 2013-11-04 12:19:57

No need for BFS or DFS, just check if the graph satisfies certain properties (to be exact, 2) and you're good to go! :)

Sourabh Verma: 2013-11-01 20:55:54

@admin Please delete Rodrigo's comment

Ouditchya Sinha: 2013-07-26 15:23:05

@Viktor Fonic : Properly written code based on bfs / dfs should give correct output for any test case. My AC code gives "NO" for your test case. :)


Added by:Thanh-Vy Hua
Date:2007-03-28
Time limit:0.166s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO
Resource:Co-author Amber