【HDOJ】1561 The more, The Better

树状DP。

 /* 1561 */
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <algorithm>
 #include <vector>
 using namespace std;

 #define MAXN 205

 vector<int> tb[MAXN];
 int dp[MAXN][MAXN];
 int a[MAXN];
 int n, m;

 int max(int a, int b) {
     return a>b ? a:b;
 }

 void init() {
     int i, j, k;

     for (i=; i<=n; ++i)
         tb[i].clear();
     memset(dp, , sizeof(dp));
 }

 void dfs(int u, int t) {
     int i, j, k, tmp;
     int v;

     if (t <= )
         return ;

     for (i=; i<tb[u].size(); ++i) {
         v = tb[u][i];
         dfs(v, t-);
         for (j=t; j>=; --j) {
             for (k=; k<=j; ++k) {
                 dp[u][j] = max(dp[u][j], dp[v][k]+dp[u][j-k]);
             }
         }
     }
     if (u) {
         for (i=m; i>=; --i)
             dp[u][i] = dp[u][i-] + a[u];
     }
 }

 int main() {
     int i, j, k;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
     #endif

     a[] = ;
     while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
         for (i=; i<=n; ++i) {
             scanf("%d %d", &j, &a[i]);
             tb[j].push_back(i);
         }
         dfs(, m);
         printf("%d\n", dp[][m]);
         init();
     }

     return ;
 }