貪心

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <iomanip>
using namespace std;

#define MAX 1000+10
struct Pie
{
    double store;
    double totalprice;
    double price;
} pie[MAX];

int cmp(const void*a, const void *b)
{
    return (*(Pie*)a).price < (*(Pie*)b).price?1:-1;
}

int main()
{
    //freopen("in.txt", "r", stdin);
    //freopen("out.txt", "w", stdout);
    int n = 0, need = 0;
    double total = 0;
    cin >> n >> need;
    for (int i = 0; i < n; i++)
        cin >> pie[i].store;
    for (int i = 0; i < n; i++)
    {
        cin >> pie[i].totalprice;
        pie[i].price = pie[i].totalprice/pie[i].store;
    }

    qsort(pie, n, sizeof(pie[0]), cmp);

    for (int i = 0; i < n; i++)
    {
        if (need - pie[i].store > 0)
        {
            total += pie[i].totalprice;
            need -= pie[i].store;
        }
        else
        {
            total += need/pie[i].store * pie[i].totalprice;
            break;
        }
    }

    cout << setprecision(2) << fixed << total;
    return 0;
}