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
itsshubham_m12: 2019-04-22 17:12:34

Is the graph directed or not??

ll14: 2019-03-15 00:05:27

If you're using Java and has the TLE, please never use Scanner instead of BufferReader

mynk322: 2019-03-13 10:10:24

Tree is undirected!
Only check for 2 cases :-
1) e=n-1
2) Only 1 conected component!

haiderbaig: 2019-03-06 10:24:51

Very good introduction to DFS.
2 points to keep in mind:
* a tree has no cycles
* a tree has no isolated node

knir0103: 2019-03-05 02:51:04

test cases 've been fixed to be undirected

Last edit: 2019-03-05 02:51:18
akashbhalotia: 2019-01-20 11:59:39

AC in java. Simple DSU. Only create DSU if M=N-1, else you will get TLE.

sunny: 2019-01-19 19:16:03

TLE on spoj. Same problem AC on codechef. On codechef time shown is 0.08s taken for AC. WTF!!

dkkv0000: 2019-01-19 18:38:14

beware graph is directed!!!!

Last edit: 2019-01-19 18:38:23
gaurav_2000: 2019-01-14 15:48:32

GRAPH IS DIRECTED.
GOT WA 5 TIMES.
Try on Test Case
6 5
1 4
2 4
3 4
5 4
5 6
Ans- No

Last edit: 2019-01-19 05:51:24
malcolm123_ssj: 2019-01-06 07:24:40

Check for two conditions:
1) n = e+1
2) The graph has only one connected component.

If condition 1 is false, then it isn't a tree. If condition 1 is true, then check for condition 2. If condition 2 is true, then the graph is a tree. Otherwise, the graph isn't a tree.

Simple AC in one go :D


Added by:Thanh-Vy Hua
Date:2007-03-28
Time limit:0.5s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO
Resource:Co-author Amber