PAT (Advanced) 1070. Mooncake (25)

#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>

using namespace std;

const int MAX = 1010;

struct Mooncake
{
	double inventory;
	double price;
	double cp;		// cost performance
	bool operator < (const Mooncake &a) const
	{
		return cp > a.cp;
	}
}mooncake[MAX];

int main()
{
	int N, D;
	cin >> N >> D;
	for (int i = 0; i < N; i++)
		cin >> mooncake[i].inventory;
	for (int i = 0; i < N; i++)
		cin >> mooncake[i].price;
	for (int i = 0; i < N; i++)
		mooncake[i].cp = mooncake[i].price / mooncake[i].inventory;
	sort(mooncake, mooncake + N);
	
	double sum = 0;
	int i = 0;
	while (D > 0 && i <= N)
	{
		int v;
		if (D <= mooncake[i].inventory)
			v = D;
		else
			v = mooncake[i].inventory;
		sum += v * mooncake[i].cp;
		D -= v;
		i++;
	}
	cout << fixed << setprecision(2) << sum << endl;

	return 0;
}