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
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RADHE SHYAM LODHI:
20160112 05:10:29
AC union set 0.00 .. 

dokz:
20160106 06:33:31
Got AC. Just run the single DFS:


Deepak :
20151230 12:34:06
thanks @rahul for your hint 

AASHISH KUMAR:
20151225 10:01:02
AC in one go :) yeyii 

rahul:
20151223 19:29:15
i think this question can be solved easily if you focus on checking how many connected component it has if it has one connected component and edges=nodes1 it will b accepted 

ankurverma1994:
20151223 15:22:25
Got AC with Union Find in 1st Attempt in Java. Don't know why its showing WA when using DFS in Java and getting AC(using same DFS code as in Java) in C++ with same logic... :( 

MAYANK NARULA:
20151208 09:41:20
Well This problem gave me some WAs .!!!!.... Maybe Graph has Self  loops at some vertices.. 

sarthak_8:
20151204 22:14:22
Yeaahh !! Finally got an AC After 3 WA. People who are new to graph (as I was) should try to look how to implement a graph and then check the ewquired conditions for a graph to be a tree. There are 3 conditions, If you want to learn try to check all 3 and not the only easiest one. Geeksforgeeks has a similar question, you can view it to understand the working of graphs.


karthik1997:
20151121 14:23:58
For people


garmel:
20151113 21:27:43
I think if you aren't confortable with graphs, you should search for a solution and understand it by using the handexecution on a paper... 
Added by:  ThanhVy Hua 
Date:  20070328 
Time limit:  0.166s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JS 
Resource:  Coauthor Amber 