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
sam96:
20160610 18:18:03
HINT : A graph is a cycle if it no. of connected components=1 and edges = nodes1


and_roid:
20160608 09:33:08
My first in graph theory!!..AC in one go!!


weramajstor:
20160527 19:46:40
I have the right to vote finally vuhuuuuu! 

Mihir Saxena:
20160519 19:24:16
Getting sigsegv error, what can be the possibility?


Luis Herrera:
20160513 22:20:50
Interesting problem.


anupamwadhwa:
20160512 20:38:21
if any node is not connected to rest of nodes then it should YES or NO 

dinkar:
20160501 10:23:14
Nice problem, got to learn about union find. 

lisbecg:
20160415 03:22:32
Did you guys build the graph in order to do DFS? 

sharif ullah:
20160312 12:31:25
just use union find check if there is a loop! 

vimal:
20160306 17:12:11
accepted on codechef... WA here... :D

Added by:  ThanhVy Hua 
Date:  20070328 
Time limit:  0.5s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO 
Resource:  Coauthor Amber 