POJ_2342_树状dp

#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
using namespace std;
int happy[6050],last[6050],dp[6050][2];
vector<int> v[6050];
vector<int>::iterator it;
void dfs(int now)
{
    dp[now][1] = happy[now];
    int len = v[now].size();
    for(int i = 0;i < len;i++)  dfs(v[now][i]);
    for(int i = 0;i < len;i++)
    {
        dp[now][1] += dp[v[now][i]][0];
        dp[now][0] += max(dp[v[now][i]][0],dp[v[now][i]][1]);
    }

}
int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        memset(dp,0,sizeof(dp));
        memset(last,-1,sizeof(last));
        for(int i = 1;i <= n;i++)   scanf("%d",&happy[i]);
        int a,b;
        while(scanf("%d%d",&a,&b) && a && b)
        {
            v[b].push_back(a);
            last[a] = b;
        }
        a = 1;
        while(last[a] != -1)    a = last[a];
        dfs(a);
        printf("%d\n",max(dp[a][0],dp[a][1]));
    }
    return 0;
}