【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=0; i<=n; ++i)
        tb[i].clear();
    memset(dp, 0, sizeof(dp));
}

void dfs(int u, int t) {
    int i, j, k, tmp;
    int v;
    
    if (t <= 0)
        return ;
    
    for (i=0; i<tb[u].size(); ++i) {
        v = tb[u][i];
        dfs(v, t-1);
        for (j=t; j>=1; --j) {
            for (k=1; k<=j; ++k) {
                dp[u][j] = max(dp[u][j], dp[v][k]+dp[u][j-k]);
            }
        }
    }
    if (u) {
        for (i=m; i>=1; --i)
            dp[u][i] = dp[u][i-1] + a[u];
    }
}

int main() {
    int i, j, k;
    
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
    #endif
    
    a[0] = 0;
    while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
        for (i=1; i<=n; ++i) {
            scanf("%d %d", &j, &a[i]);
            tb[j].push_back(i);
        }
        dfs(0, m);
        printf("%d
", dp[0][m]);
        init();
    }
    
    return 0;
}