HDU 1561 The more, The Better

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<queue>
#include<vector>
#include<map>
using namespace std;
typedef long long LL;
const int INF = 1e9+7;
const int maxn = 1000;
const int MOD = 1e9+7;
int dp[maxn][maxn];///dp[第n个结点][攻克第n个结点下面的k个城堡] = 最大值
vector<vector<int> > G;
void DFS(int root,int m)
{
int len = G[root].size();

for(int i=0; i<len; i++)
{
int e = G[root][i];
if(m > 1) DFS(e, m-1);

for(int j=m; j>=2; j--)///root结点选取下面j个结点
{
for(int k=1; k < j; k++)///
dp[root][j] = max(dp[root][j], dp[root][j-k]+dp[e][k]);
}
}
}

int main()
{
int n, m;
while(scanf("%d %d", &n, &m), n+m)
{
G.clear();
G.resize(n+5);
memset(dp, 0, sizeof(dp));
for(int i=1; i<=n; i++)
{
int s, w;
scanf("%d %d", &s, &w);
G[s].push_back(i);
dp[i][1] = w;
}
DFS(0, m+1);
printf("%d\n", dp[0][m+1]);
}
return 0;
}