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EICHTTRE - Is tree

Given a graph of n vertices and m edges. Check if the given graph is a tree.

Input:

The first line contains the number of T test cases (T <100).

Each testc case includes:

  • The first line contains two positive integers, the number of vertices n (0 < n < 105) và m edges( m <= 2 x 105)
  • Then there are m lines, each containing two positive integers u and v (u,v < 105) representing an edge between node u and node v

Output:

Include T lines corresponding to the number of test cases, if the graph is a tree, print "YES" and print "NO" otherwise.

Sample:

Input :

3

6 5

0 1

0 2

1 5

2 4

2 3

5 5

0 1

0 2

1 3

3 1

3 4

4 3

0 1

1 3

0 3

Output:

YES

NO

NO


Added by:Ha Minh Ngoc
Date:2016-01-04
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: GOSU
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