zju2109

FatMouse’ Trade

http://acm.zju.edu.cn/show_problem.php?pid=2109

Time limit: 1 Seconds

Memory limit: 32768K

FatMouse prepared M pounds of cat food, ready to trade with the cats guarding the warehouse containing his favorite food, JavaBean.

The warehouse has N rooms. The i-th room contains J[i] pounds of JavaBeans and requires F[i] pounds of cat food. FatMouse does not have to trade for all the JavaBeans in the room, instead, he may get J[i]* a% pounds of JavaBeans if he pays F[i]* a% pounds of cat food. Here a is a real number. Now he is assigning this homework to you: tell him the maximum amount of JavaBeans he can obtain.

Input

The input consists of multiple test cases. Each test case begins with a line containing two non-negative integers M and N. Then N lines follow, each contains two non-negative integers J[i] and F[i] respectively. The last test case is followed by two -1’s. All integers are not greater than 1000.

Output

For each test case, print in a single line a real number accurate up to 3 decimal places, which is the maximum amount of JavaBeans that FatMouse can obtain.

Sample Input

Sample Output

13.333
31.500

/*Written by czk*/
#include <iostream>
#include <iomanip>
#include <queue>
using namespace std;
struct room{
    int java_bean;
    int cat_food;
    bool operator<(const room &r) const{
        return static_cast<double>(java_bean) / cat_food < static_cast<double>(r.java_bean) / r.cat_food;
    }
};

int main() {
    while(1) {
        int m, n;
        cin >> m >> n;
        if (m == -1 && n == -1) break;
        priority_queue<room> rooms;
        for(int i = 0; i < n; i++) {
            room r;
            cin >> r.java_bean >> r.cat_food;
            rooms.push(r);
        }
        double total = 0.0;
        while(!rooms.empty() && m > 0) {
            if(m>rooms.top().cat_food) {
                total += rooms.top().java_bean;
                m -= rooms.top().cat_food;
            } else {
                total += static_cast<double>(rooms.top().java_bean) / rooms.top().cat_food * m;
                m = 0;
            }
            rooms.pop();
        }
        cout << fixed<<setprecision(3) << total  << endl;
    }

}