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
code0monkey1:
20180406 17:31:22
DSU makes this super easy . #beware ( tot edges = tot nodes 1 , in a valid tree ) 

lefthander:
20180401 05:38:46
AC in one go ! Only DFS 0.00sec 

sanjeev:
20180328 18:34:38
solve it with dsu algorithm, you will get to know few things. 

ameyanator:
20180319 06:57:59
Solved using BFS. Conditions to keep in mind are that n==m1 for a tree. And whenever this holds true all the nodes must be connected so simply bfs :) 

naduhrin78:
20180204 05:35:59
DSU yolo 

himansh242:
20180201 15:35:12
0.01 ac!! :) 

coding_panda:
20180129 02:54:21
Killed in one go ! Disjoint Set all the way ! 

bradyawn:
20180123 20:06:24
SPOILER:


maruf_robin:
20180120 18:53:07
Keep in mind a tree must have n1 edges & all the node will be connected. 

anurag_05:
20180115 14:30:56
AC in one go... just check for cycles and whether each and every vertex is visited during DFS

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 