状态转移方程：
dp[u][0] = max(dp[v][0],dp[v][1]);
dp[u][1] += dp[v][0];
#include <iostream>
#include <cstdio>
#include <vector>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 6010;
vector<int>tree[maxn];
int rat[maxn],deg[maxn],dp[maxn][2];
int max(int x,int y){
return x > y ? x : y;
}
void dfs(int u){
if(0 == tree[u].size())
{
dp[u][1] = rat[u];
return ;
}
dp[u][1] += rat[u];
for(int i = 0; i < tree[u].size(); i++){
int v = tree[u][i];
dfs(v);
dp[u][0] += max(dp[v][0],dp[v][1]);
dp[u][1] += dp[v][0];
}
}
int main()
{
// freopen("in.txt","r",stdin);
int n,l,k,root;
while( ~scanf("%d",&n) ){
for( int i = 1; i <= n; i++){
tree[i].clear();
scanf("%d",rat+i);
}
memset(deg,0,sizeof(deg));
while( ~scanf("%d%d",&l,&k) , l||k){
deg[l]++;
tree[k].push_back(l);
}
memset(dp,0,sizeof(dp));
for( root = 1; root <= n; root ++){
if( !deg[root]){
dfs(root);
break;
}
}
printf("%d
",max(dp[root][0],dp[root][1]));
}
return 0;
}