p4322 [JSOI2016]最佳团体

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<cctype>
#include<cmath>
#include<cstdlib>
#include<queue>
#include<ctime>
#include<vector>
#include<set>
#include<map>
#include<stack>
using namespace std;
int n,m;
int s[5000],p[5000],r[5000],siz[2505];
double dp[2505][2505];
vector<int>v[5000];
inline void go(int x,double mid){
    dp[x][1]=double(p[x]-s[x]*mid);
    siz[x]=1;
    for(int i=0;i<v[x].size();i++){
      go(v[x][i],mid);
      for(int j=siz[x];j>0;j--)
        for(int k=0;k<=siz[v[x][i]];k++)
          dp[x][j+k]=max(dp[x][j+k],dp[x][j]+dp[v[x][i]][k]);
      siz[x]+=siz[v[x][i]];
    }
}
inline bool ck(double mid){
    memset(dp,-10,sizeof(dp));
    s[0]=p[0]=0;
    go(0,mid);
    return dp[0][m+1]>=0;
}
signed main(){
    int i,j,k;
    scanf("%d%d",&m,&n);
    for(i=1;i<=n;i++){
      scanf("%d%d%d",&s[i],&p[i],&r[i]);
      v[r[i]].push_back(i);
    }
    double le=0,ri=10000.0001;
    while(ri-le>0.0001){
      double mid=(le+ri)/2;
      if(ck(mid))le=mid;
        else ri=mid;
    }
    printf("%0.3lf\n",le);
    return 0;
}