hdu 1561 树形DP

题意就不说了，中文题都懂的。这是我的第一道树形DP，还是看了别人的解题报告才做的。

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 1 #include <stdio.h>
 2 #include <string.h>
 3 #define MAX(a,b) (a)>(b)?(a):(b)
 4 #define N 205
 5 struct node {
 6     int from,to,next;
 7 }edge[N];
 8 int dp[N][N],visit[N],val[N],head[N],n,m,tol;
 9 void add(int a,int b)
10 {
11     edge[tol].from = a;
12     edge[tol].to = b;
13     edge[tol].next = head[a];
14     head[a] = tol++;
15 }
16 void dfs(int root)
17 {
18     int i,j,k,u;
19     visit[root] = 1;
20     for(i = head[root];i != -1;i = edge[i].next)
21     {
22         u = edge[i].to;
23         if(!visit[u])
24         {
25             dfs(u);
26             for(k = m+1;k >= 2; --k)
27                 for(j = 1;j < k; ++j)
28                     dp[root][k] = MAX(dp[root][k],dp[root][k-j]+dp[u][j]);
29         }
30     }
31 }
32 int main()
33 {
34     int i,a,b;
35     while(~scanf("%d %d",&n,&m) && n && m)
36     {
37         tol = 0;
38         memset(head,-1,sizeof(head));
39         memset(visit,0,sizeof(visit));
40         memset(dp,0,sizeof(dp));
41         for(i = 1;i <= n; ++i)
42         {
43             scanf("%d %d",&a,&b);
44             val[i] = b;
45             add(a,i);
46             dp[i][1] = b;
47         }
48         val[0] = 0;
49         dfs(0);
50         printf("%d\n",dp[0][m+1]);
51     }
52     return 0;
53 }