1 #include<stdio.h>
2 #include<string.h>
3 #include<math.h>
4 #include<algorithm>
5 using namespace std;
6 int son[6005],dp[6005][3],father[6005],f[6005][6005],a[6005];
7 void dfs(int x)
8 {
9 if (son[x]==0){
10 dp[x][0]=0; dp[x][1]=a[x];
11 return;
12 }
13 dp[x][1]=a[x];
14 dp[x][0]=0;
15 for (int i=1;i<=son[x];i++)
16 {
17 dfs(f[x][i]);
18 dp[x][1]+=dp[f[x][i]][0];
19 dp[x][0]+=max(dp[f[x][i]][1],dp[f[x][i]][0]);
20 }
21 }
22 int main()
23 {
24 int n,i,j,x,y,sum;
25 while (~scanf("%d",&n))
26 {
27 for (i=1;i<=n;i++)
28 scanf("%d",&a[i]);
29 memset(son,0,sizeof(son));
30 memset(father,0,sizeof(father));
31 while (~scanf("%d%d",&x,&y)&&x&&y)
32 {
33 son[y]++;
34 f[y][son[y]]=x;
35 father[x]=y;
36 }
37 for (i=1;i<=n;i++)
38 if (father[i]==0) dfs(i);
39 sum=0;
40 for (i=1;i<=n;i++)
41 if (father[i]==0)
42 sum+=max(dp[i][0],dp[i][1]);
43 printf("%d\n",sum);
44 }
45 }
http://acm.hdu.edu.cn/showproblem.php?pid=1520
