poj1655

/***************************************************************\

 *Author:Hu Wenbiao

 *Created Time: Tue 17 Aug 2010 04:54:15 PM CST

 *File Name: main.cpp

 *Description:树状dp。邻接表

\***************************************************************/

//*========================*Head File*========================*\\



#include<iostream>

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

/*----------------------*Global Variable*----------------------*/

int dp[20010], first[20010], tot, t, N, a, b;

struct Edge {

    int next, to;

} edge[40010];

//*=======================*Main Program*=======================*//

using namespace std;



void insertedge(int a, int b)

{				//添加边(a,b),(b,a)

    edge[tot].to = b;

    edge[tot].next = first[a];

    first[a] = tot++;

    edge[tot].to = a;

    edge[tot].next = first[b];

    first[b] = tot++;

}



int tree_dp(int from, int now)

{				//现在结点now，它的父结点是from

    //sum记录now为根的子树的结点数，_max记录now各个子树最大结点数

    int p = first[now], to;

    int _max = 0, sum = 1, tmp;

    while (p != -1) {

	to = edge[p].to;

	p = edge[p].next;

	if (to == from)

	    continue;

	tmp = tree_dp(now, to);

	if (_max < tmp)

	    _max = tmp;

	sum += tmp;

    }

    dp[now] = N - sum > _max ? N - sum : _max;

    return sum;

}



int main()

{

    //freopen("input","r",stdin);

    scanf("%d", &t);

    while (t--) {

	memset(first, -1, sizeof(first));

	tot = 0;

	scanf("%d", &N);

	for (int i = 1; i < N; i++) {

	    scanf("%d%d", &a, &b);

	    insertedge(a, b);

	}

	tree_dp(0, 1);

	int ans, _min = N;

	for (int i = 1; i <= N; i++) {

	    if (dp[i] < _min) {

		_min = dp[i];

		ans = i;

	    }

	}

	printf("%d %d\n", ans, dp[ans]);

    }

}

Source Code