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