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
akashbhalotia:
20190120 11:59:39
AC in java. Simple DSU. Only create DSU if M=N1, else you will get TLE. 

sunny:
20190119 19:16:03
TLE on spoj. Same problem AC on codechef. On codechef time shown is 0.08s taken for AC. WTF!! 

dkkv0000:
20190119 18:38:14
beware graph is directed!!!! Last edit: 20190119 18:38:23 

gaurav_2000:
20190114 15:48:32
GRAPH IS DIRECTED.


malcolm123_ssj:
20190106 07:24:40
Check for two conditions:


artistic_15:
20181229 20:05:48
Easy Union Find Implementation. 

suyashky:
20181127 08:40:39
learned a lot....good question for beginners.


themast3r:
20180922 18:44:52
Simple Disjoint Set Union gets AC! 

harry_shit:
20180919 12:54:03
can someone tell me what will be the start node.is it 1?? 

phoemur:
20180912 00:58:36
Beware Adjacency Matrix will most likely TLE.

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 