Sphere Online Judge

SPOJ Problem Set (classical)

1436. Is it a tree

Problem code: PT07Y


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

Added by:Thanh-Vy Hua
Date:2007-03-28
Time limit:1s
Source limit:50000B
Memory limit:256MB
Cluster: Pyramid (Intel Pentium III 733 MHz)
Languages:All except: ERL JS
Resource:Co-author Amber

hide comments
2014-03-29 21:25:37 Anubhav Balodhi
Easier than I thought... agreed with both the points of @Rastogi..
2014-03-17 11:59:31 Anuj Yadav
No need for BFS or DFS !! easy one .
2014-03-06 04:51:00 californiagurl
for a given test case can multiple edges exist between two nodes?
is the best method similar to kruskal's MST algo or DFS/BFS?

Last edit: 2014-03-06 16:48:52
2014-02-13 19:23:19 hiddenman
easy 1..... :)
2014-02-02 08:25:13 sonam
mai DFS use kar rahi hu to wo to O(2*E) me ho jata hai to phir TLE kyo plz tell me.mai bahut dino se try kar rahi hu
2014-02-02 08:22:23 sonam
i am using adjecency list and use DFS.
still i m getting TLE.can any one tell me why plzzzzzzzzzzz.
2014-01-21 16:41:12 Shubham Sharma
Very Weak test cases !
2014-01-10 23:52:01 adze
@Paul Draper
answer for test case
4 3
1 2
3 4
1 3
is YES, no need to build tree in order
2013-12-10 15:00:16 Bhavik
kindly check my solution id:10630933
giving WA..don't know why?
2013-11-13 16:31:12 Avaneesh Rastogi
1) The number of nodes should be raised to a million with the same time limit, to reject solutions which apply a sub-optimal approach
2) Weak test cases should be fixed as reported by other coders.
© Spoj.com. All Rights Reserved. Spoj uses Sphere Engine™ © by Sphere Research Labs.