PT07X - Vertex Cover

You are given an unweighted, undirected tree. Write a program to find a vertex set of minimum size in this tree such that each edge has as least one of its end-points in that set.


The first line of the input file contains one integer N --- number of nodes in the tree (0 < N <= 100000). Next N-1 lines contain N-1 edges of that tree --- Each line contains a pair (u, v) means there is an edge between node u and node v (1 <= u,v <= N).


Print number of nodes in the satisfied vertex set on one line.

Example 1

1 2
1 3


The set can be {1}

Example 2

1 2
2 3


The set can be {2}

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abhi6991: 2017-09-23 05:40:13

In Cpp not passing graph as a reference resulted in 2 WA.

mamnoonsiam: 2017-07-25 13:07:30

AC in one go :)
easy tree dp... dfs

d_skyhawk: 2017-04-01 06:45:04

DP+Tree=AC in a go

rishi_07: 2017-03-31 15:48:01

Finally AC! Nice DP.

cake_is_a_lie: 2017-03-05 14:44:08

For some reason I understood each vertex needed one neighbour in the output set. That cost me SO many WAs.

siddharth9820: 2017-02-19 09:27:54

Isnt it a straight divide and conquer problem?

sina_ss: 2017-02-14 18:03:23

it is so badihi

Last edit: 2017-02-14 18:53:24
vengatesh15: 2016-12-23 06:50:41

AC in 1 go :-)

lt: 2016-11-27 14:51:55

Greedy is failing in very particular cases, while DP is awesome! :D

Last edit: 2016-11-27 14:52:50
kartikay singh: 2016-06-30 18:05:47

Tried with dp,greedy and maximum matching ... :-D

Added by:Thanh-Vy Hua
Time limit:0.194s-1.254s
Source limit:50000B
Memory limit:1536MB
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Resource:Co-author Amber