poj 2342Anniversary party（树形dp）

最新推荐文章于 2019-11-24 23:57:32 发布

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本文介绍了一个用于大学80周年庆典挑选嘉宾的算法。该算法旨在最大化嘉宾的亲和力评分总和，同时确保没有员工及其直接上司同时出席。通过递归深度优先搜索遍历员工层级结构，并使用动态规划来解决此问题。

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Anniversary party

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 4594		Accepted: 2607

Description

There is going to be a party to celebrate the 80-th Anniversary of the Ural State University. The University has a hierarchical structure of employees. It means that the supervisor relation forms a tree rooted at the rector V. E. Tretyakov. In order to make the party funny for every one, the rector does not want both an employee and his or her immediate supervisor to be present. The personnel office has evaluated conviviality of each employee, so everyone has some number (rating) attached to him or her. Your task is to make a list of guests with the maximal possible sum of guests' conviviality ratings.

Input

Employees are numbered from 1 to N. A first line of input contains a number N. 1 <= N <= 6 000. Each of the subsequent N lines contains the conviviality rating of the corresponding employee. Conviviality rating is an integer number in a range from -128 to 127. After that go N – 1 lines that describe a supervisor relation tree. Each line of the tree specification has the form:
L K
It means that the K-th employee is an immediate supervisor of the L-th employee. Input is ended with the line
0 0

Output

Output should contain the maximal sum of guests' ratings.

Sample Input

Sample Output

Source

Ural State University Internal Contest October'2000 Students Session

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<set>
#include<map>

#define L(x) (x<<1)
#define R(x) (x<<1|1)
#define MID(x,y) ((x+y)>>1)

#define eps 1e-8
typedef __int64 ll;

using namespace std;

#define N 6005
int n;

int dp[N][2],vis[N],father[N];

void dfs(int x)
{
	int i,j;
	vis[x]=1;
	for(i=1;i<=n;i++)
		if(!vis[i]&&father[i]==x)
		{
			dfs(i);
			dp[x][1]+=dp[i][0];
			dp[x][0]+=max(dp[i][0],dp[i][1]);
		}
}

int main()
{
	int i,j;
	while(~scanf("%d",&n))
	{
		memset(dp,0,sizeof(dp));
		memset(vis,0,sizeof(vis));
		memset(father,0,sizeof(father));

		for(i=1;i<=n;i++)
			scanf("%d",&dp[i][1]);

		int e,s;

		while(scanf("%d%d",&s,&e),s+e)
		{
			 father[s]=e;
		}

		i=1;

		while(father[i])
			i=father[i];

		dfs(i);

		printf("%d\n",max(dp[i][1],dp[i][0]));

	}
	return 0;
}