hdu 1009 FatMouse' Trade

Sample Input

5 3

7 2

4 3

5 2

20 3

25 18

24 15

15 10

-1 -1

Sample Output

13.333

31.500

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

using namespace std;

struct FoodTrade
{
int catFood;
int javaBean;
double rate;
};

bool cmp(FoodTrade x, FoodTrade y)
{
return x.rate > y.rate;
}

class FatMouseTrade
{
public:
void initialize();
void readCase(const int& m, int& n);
void compute();
void output();
private:
int catFood;
vector<FoodTrade> foodTrade;
double amount;
};

void FatMouseTrade::initialize()
{
catFood = 0;
amount = 0;
foodTrade.clear();
}

void FatMouseTrade::readCase(const int& m, int& n)
{
catFood = m;
while(n--)
{
FoodTrade food;
cin >> food.javaBean >> food.catFood;
food.rate = static_cast<double>(food.javaBean) / food.catFood;
foodTrade.push_back(food);
}
}

void FatMouseTrade::compute()
{
sort(foodTrade.begin(), foodTrade.end(), cmp);
for(int i = 0; i < foodTrade.size() && catFood != 0; ++i)
{
if(catFood < foodTrade[i].catFood)
{
amount += foodTrade[i].rate * catFood;
catFood = 0;
}
else
{
catFood -= foodTrade[i].catFood;
amount += foodTrade[i].javaBean;
}
}
}

void FatMouseTrade::output()
{
cout << setprecision(3) << setiosflags(ios::showpoint) << setiosflags(ios::fixed) << amount << endl;
}

int main()
{
FatMouseTrade fatMouseTrade;
int m, n;
while(cin >> m >> n && m != -1 && n != -1)
{
fatMouseTrade.initialize();
fatMouseTrade.readCase(m, n);
fatMouseTrade.compute();
fatMouseTrade.output();
}
return 0;
}贪心算法