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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Anurag Pasi:
20150630 13:39:28
Implementation of DFS by Adjacency list+STL 0.00 sec and 3.4Mb :)


gamer496:
20150629 19:36:41
@Sukeesh YES 

r0bo_dart:
20150622 13:47:25
AC in 2nd go... read the method of finding connected components. Good question 

Sukeesh:
20150614 19:41:40
input :


Linus:
20150611 21:59:22
Very good question ..learned a lot ...read this .... https://www.cs.princeton.edu/~rs/AlgsDS07/01UnionFind.pdf .....The way here union find is described is just awesome .... my 25 !!!!!


peeyush taneja:
20150611 20:12:42
NIce question 

mayank:
20150608 23:30:52
They are not checking for edge disconnectivity in graph (ie. already given m=n1).Good problem though.


Manish Sombansh:
20150605 10:18:35
I am trying to solve this problem using unionfind. but am getting TLE. Can anybody please tell me what's the error? My source code : http://ideone.com/EogUfW 

BRAIN:
20150604 16:26:13
using dfs or bfs to check connect and using FindSet and Union of Kruskal algorithm to check circle 

Shubham Khilari:
20150529 17:52:14
my first problem in graphs. solved in O(n^2).Did not use any stl or dfs bfs.Just try to find if there is a cycle or not..and then u r done.Executes in 0.09.Is there a faster way?

Added by:  ThanhVy Hua 
Date:  20070328 
Time limit:  0.166s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel Pentium G860 3GHz) 
Languages:  All except: ERL JS 
Resource:  Coauthor Amber 