PAT (Advanced) 1070. Mooncake (25)

原题：1070. Mooncake (25)

解题思路：

贪心。每次挑单价最高的即可。注意质量用double保存，不然第三个样例过不去。

代码如下：

#include<cstdio>
#include<algorithm>
using namespace std;
const int maxn = 1000 + 5;
struct MC
{
    double price;
    double amt;
    bool operator < (const MC& rhs)
    {
        return price / amt > rhs.price / rhs.amt;
    }
} mooncake[maxn];

int main()
{
    int n;
    double m;
    while(scanf("%d %lf", &n, &m) == 2)
    {
        for(int i = 0; i < n; i++) scanf("%lf", &mooncake[i].amt);
        for(int i = 0; i < n; i++) scanf("%lf", &mooncake[i].price);
        sort(mooncake, mooncake + n);
        double ans = 0;
        int idx = 0;
        while(m > 0 && idx < n)
        {
            if(m >= mooncake[idx].amt)
            {
                m -= mooncake[idx].amt;
                ans += mooncake[idx].price;
            }
            else
            {
                ans += mooncake[idx].price / mooncake[idx].amt * m;
                m = 0;
            }
            idx++;
        }
        printf("%.2f\n", ans);
    }
    return 0;
}