UVA 10417 Gift Exchanging

题意：对于概率很无解，参考：点击打开链接

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;

double p[20][20];
int num[10];
int N;
double ans;

void dfs(int cur,double cp){
    if (cur == N){
        ans += cp;
        return;
    }
    for (int i = 0; i < 5; i++){
        if (num[i] == 0)
            continue;
        if (p[cur][i] == 0.0)
            continue;
        num[i]--;
        dfs(cur+1,cp*p[cur][i]);
        num[i]++;
    }
}

int main(){
    int t;
    scanf("%d",&t);
    while (t--){
        scanf("%d",&N);
        for (int i = 0; i < 5; i++)
            scanf("%d",&num[i]);
        for (int i = 0; i < N; i++)
            for (int j = 0; j < 5; j++)
                scanf("%lf",&p[i][j]);
        double Max = 0.0;
        int id;
        double sum = 0.0;
        for (int i = 0; i < 5; i++){
            if (num[i] == 0)
                continue;
            num[i]--;
            ans = 0.0;
            dfs(1,1.0);
            ans *= p[0][i];
            sum += ans;
            num[i]++;
            if (Max < ans/num[i]){
                Max = ans/num[i];
                id = i;
            }
        }
        printf("%d %.3lf\n",id+1,Max/sum);
    }
    return 0;
}