POJ 2342

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
#define maxn 6000+5
int n,rat[maxn],fa[maxn],dp[maxn][2],vis[maxn];
void dfs(int x )
{
  vis[x] = 1;
  for(int i = 1;i <= n;i ++)
  {
    if(!vis[i] && fa[i] == x)
    {
      dfs(i);
      dp[x][0] += max(dp[i][0], dp[i][1]);
      dp[x][1] += dp[i][0] ;
    }
  }
}
int main()
{
    while(scanf("%d", &n) != EOF)
    {
     int a,b,root;
     memset(vis, 0, sizeof(vis));
     memset(fa, 0, sizeof(fa));
     for(int i = 1;i <= n;i ++)
     scanf("%d", &rat[i]);
     for(int i = 1;i <= n-1;i ++)
     {
       scanf("%d%d", &a, &b);
       fa[a] = b;
     }
     scanf("%d%d", &a, &b);
     for(int i = 1;i <= n;i ++)
     {
       if(fa[i] == 0) root = i;
       dp[i][0] = 0;
       dp[i][1] = rat[i];
     }
     dfs(root);
     printf("%d\n",max(dp[root][0],dp[root][1]));
    }
    return 0;
}