hdu1561 树形dp + 背包

#include<cstdio>
#include<cstring>
#include<iostream>
#define INF 999999999
using namespace std;
const int MAXN = ;
struct node
{
    int to;
    int v;
    int next;
}edge[MAXN*];
int pre[MAXN],n,index,vis[MAXN],m,num[MAXN];
int dp[MAXN][MAXN];
int max(int x,int y)
{
    return x>y?x:y;
}
void add(int x,int y,int z)
{
    edge[index].to = y;
    edge[index].v = z;
    edge[index].next = pre[x];
    pre[x] = index++;
}
void dfs(int root)
{
    int j,k;
    vis[root] = ;
    for(int i=pre[root]; i!=-; i=edge[i].next){
        int t = edge[i].to;
        if(!vis[t]){
            dfs(t);
            for(j=m+; j>=; j--){
                for(k=; k<j; k++){
                    dp[root][j] = max(dp[root][j], dp[root][k] + dp[t][j-k]);
                }
            }
        }
    }
}
int main()
{
    int i,j;
    while(~scanf("%d%d",&n,&m))
    {
        if(!n&&!m)break;
        index = ;
        memset(num,,sizeof(num));
        memset(pre,-,sizeof(pre));
        memset(dp,,sizeof(dp));
        memset(vis,,sizeof(vis));
        for(i=; i<=n; i++){
            int x, y;
            scanf("%d%d",&x,&y);
            num[x] ++;
            add(i, x, y);
            add(x, i, y);
            for(j=; j<=m; j++){
                dp[i][j] = y;
            }
        }

        dfs();
        printf("%d\n",dp[][m+]);
    }
}