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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madhavgaba:
20161220 08:33:04
Use the fact that a tree has n1 edges and DFS from one node visits all the nodes........green in first go;) 

gyanchand:
20161219 18:16:48
use adjacency list instead of adjacency matrix @reconnect as v*v>>e i.e. it will be sparse matrix.lead to waste of time on traversing.


praney_rai:
20161219 08:39:33
did it using simple bfs!! first graph problem :] (out of the world feeling :D) 

nikunjsoni:
20161213 15:29:11
Check the condition of N = 1 

dongntk54:
20161211 10:37:33
. Last edit: 20161211 11:14:53 

vengatesh15:
20161210 14:08:03
Simple DFS


vishal_khanna:
20161204 15:41:18
I'm getting WA for test 6. How do I know if my code is correct or not? 

nimmumanoj:
20161204 10:46:42
So easy. You don't have to use map. The nodes are numbered from 1 to N. 

syed_tanveer:
20161126 09:56:23
My 50th, did it using unionfind. 

reconnect:
20161124 23:17:50
i am getting a TLE. I am using BFS . Can anybody please suggest the error. Is this because of the adjacency matrix? Last edit: 20161124 23:19:10 
Added by:  ThanhVy Hua 
Date:  20070328 
Time limit:  0.166s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO 
Resource:  Coauthor Amber 