POJ 2342 树状dp

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<cstdio>
 6 using namespace std;
 7 const int maxn=6007;
 8 bool visit[maxn];
 9 int value[maxn];
10 int head[maxn];
11 int dp[maxn][2];
12 int sum=0;
13 int n;
14 struct node
15 {
16     int to,next;
17 };
18 node tree[maxn];
19 void init()
20 {
21     memset(head,-1,sizeof(head));
22     memset(visit,0,sizeof(visit));
23     memset(dp,0,sizeof(dp));
24     memset(value,0,sizeof(value));
25     sum=0;
26 }
27 void AddEdge(int u,int v)
28 {
29         tree[sum].to=v;
30         tree[sum].next=head[u];head[u]=sum;
31         sum++;
32 }
33 void dfs_tree(int point)
34 {
35     int res0=0,res1=0;
36     if(visit[point]) return;
37     visit[point]=1;
38     for(int i=head[point];i!=-1;i=tree[i].next)
39     {
40         if(!visit[tree[i].to]) dfs_tree(tree[i].to);
41         res1+=dp[tree[i].to][0];
42         res0+=max(dp[tree[i].to][0],dp[tree[i].to][1]);
43     }
44     dp[point][0]=res0;
45     dp[point][1]=res1+value[point];
46 }
47 int main()
48 {
49     // freopen("in.txt","r",stdin);
50     while(~scanf("%d",&n)){
51         init();
52         for(int i=1;i<=n;i++)
53         {
54             scanf("%d",&value[i]);
55         }
56         int a,b;
57         while(1)
58         {
59             scanf("%d %d",&a,&b);
60             if(a==0&&b==0) break;
61             AddEdge(b,a);
62             visit[a]=1;
63         }
64         int root;
65         for(int i=1;i<=n;i++)
66         {
67             if(visit[i]==0) root=i;
68         }
69         memset(visit,0,sizeof(visit));
70         dfs_tree(root);
71         int ans=max(dp[root][0],dp[root][1]);
72         printf("%d\n",ans);
73     }
74     return 0;
75 }