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
sayasaiteja: 2017-12-12 15:58:49

AC in one GO!!

abhar10: 2017-11-14 08:15:54

My 50th!!
AC in one Go!!
Solved using Union-Find

punee901: 2017-10-26 14:36:12

java people use input method other than scanner class it gives me one tle.
just use Adjacency List and dfs.

g_o_d: 2017-10-22 10:24:57

It can also also be solved as follow:
Just check whether both edges you are taking as input is already present or not.

vicky_1998: 2017-10-19 13:02:25

Just Disjoint Set works quite well

hemant1612: 2017-10-03 17:53:33

cool problem

msd_007: 2017-08-27 16:59:31

what if test cases contain self loops ??
even if we run a dfs and check if(m==n-1&&all nodes are visited) ..we print yes bt actually it should be no ri8 ??
can anyone clarify dis ??

supriyanta: 2017-08-14 23:38:02

Run dfs only once. Then check whether all the vertices are visited and no of edges equals no of vertices minus one.

supriyanta: 2017-08-14 13:10:27

bfs or dfs or union find.But you have to consider the disconnected graphs also, which are not trees.

vishesh197: 2017-08-13 20:12:03

my code got accepted on codechef but was'nt accepted by spoj


Added by:Thanh-Vy Hua
Date:2007-03-28
Time limit:0.166s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO
Resource:Co-author Amber