InputEmployees 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 T lines that describe a supervisor relation tree. Each line of the tree specification has the form:

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

水題一道，晚安。

#include<cstdio>
#include<cstdlib>
#include
 
<cstring>
#include<iostream>
#include<algorithm>
#include<memory>
using namespace std;
const int maxn=20000;

int vis[maxn],V[maxn],ans,cnt,dp[maxn][2];
int Laxt[maxn],Next[maxn],To[maxn],ru[maxn];

void add(int u,int v){
    Next[++cnt]=Laxt[u];
    Laxt[u]=cnt;
    To[cnt]=v;
}

int dfs(int u)
{
    vis[u]=1;
    dp[u][1]=V[u];
    for(int i=Laxt[u];i;i=Next[i]){
         int v=To[i];
         if(!vis[v]){
            dfs(v);
            dp[u][1]+=dp[v][0];
            dp[u][0]+=max(dp[v][0],dp[v][1]);
         }
    }
}

int main()
{
    int i,j,k,n,u,v;
    while(~scanf("%d",&n)){
        cnt=0;ans=0;
        memset(Laxt,0,sizeof(Laxt));
        memset(dp,0,sizeof(dp));
        memset(ru,0,sizeof(ru));
        memset(vis,0,sizeof(vis));
        for(i=1;i<=n;i++) scanf("%d",&V[i]);
        for(;;){
           scanf("%d%d",&u,&v);
           if(u==0&&v==0) break;
           add(v,u);
           ru[u]++;
        } 
        for(i=1;i<=n;i++) {
          if(ru[i]==0) {
              dfs(i);
              ans+=max(dp[i][1],dp[i][0]);//防止多棵樹 
          }
         } 
        printf("%d\n",ans);
    }
    return 0;
}

HDU1520 Anniversary party 樹形DP基礎