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
harva12: 2017-07-17 22:25:40


Last edit: 2017-07-17 23:28:16
imranjeetsingh: 2017-07-13 14:05:38

you just need to know what is a tree topology. Thereafter it is a cakewalk.

nikhil2504: 2017-07-10 09:50:21

Connected and |e|=|v|-1 !

jayu_jd: 2017-07-06 17:29:26

Nice Question.!!
check for parent and unvisited nodes.

rakib77: 2017-06-24 01:21:57

Use Disjoint Set, Straightforward :D AC in One Go

quantic: 2017-06-20 14:43:40

cases are too weak.

cichipi_: 2017-06-12 11:59:38

if(m!=n-1 || n==1)cout<<"NO";

then run dfs....check cycle...if not YES else no

AC!!...easy

hazanko: 2017-06-06 08:56:27

I'm getting a null pointer error flagged at the line where I read the first input line with bufferedreader... Weird thing is that Codechef also offers this problem so I plugged it in there and got AC in one go. Anyone else having this issue?

syamphanindra: 2017-05-23 18:27:35

Take care to check all nodes are visited or not it gave me 3 WA so check it

Rajat Gautam: 2017-05-20 00:29:49

Used BFS once , if no. of edges is less than no. of vertex. And any one or more than one node remained unvisited after BFS then there is a cycle for sure because then there will be n-1 edges and n-1 vertex and 1 vertex separated.


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