poj 2342 Anniversary party 树形dp入门

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
7
1
1
1
1
1
1
1
1 3
2 3
6 4
7 4
4 5
3 5
0 0
Sample Output
5

题意：有n个人，接下来n行是n个人的价值，再接下来n行给出l，k说的是l的上司是k，这里注意l与k是不能同时出现的
dfs到根再回溯。
考虑根和叶子的关系，如果 上司去，那么下属不能去，如果上司不去，下属有去或者不去两种方式。

#include <iostream>#include <cstdio>#include <cstring>using namespace std;int dp[6010][2];int vis[6010];int father[6010];int n;void dfs(int x){    vis[x]=1;    for(int 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(){    while(scanf("%d",&n)!=EOF)    {    for(int i=1;i<=n;i++)    {        scanf("%d",&dp[i][1]);    }    int a,b;    int root=0;    while(scanf("%d%d",&a,&b),a+b>0)    {        father[a]=b;        root=b;    }    memset(vis,0,sizeof(vis));    dfs(root);    printf("%d\n",max(dp[root][0],dp[root][1]) );}}