FatMouse' Trade (贪心)

 

 

 

#include <iostream>
#include <stdio.h>
#include <cstring>
#include <cmath>
#include <algorithm>


using namespace std;

struct node
{
    double J;        // JavaBean
    double F;        // Food
    double rate;    // 性价比 
}arr[1000];

bool cmp(node a, node b)
{
    return a.rate > b.rate;
}

int main() 
{
    int m, n;
    double a, b;
    while(cin >> m >> n)
    {
        if(m == -1 && n == -1)
            break;
        
        for(int i = 0; i < n; ++i)
        {
            cin >> arr[i].J >> arr[i].F;
            arr[i].rate = (arr[i].J) / (arr[i].F);
        }
        
        sort(arr, arr+n, cmp);
        
        double ans = 0;
        for(int i = 0; i < n; ++i)
        {
            if(m > arr[i].F)
            {
                ans += arr[i].J;
                m -= arr[i].F;
            }
            else
            {
                ans += m*arr[i].rate;
                break;
            }
            
        }
        
        printf("%0.3f\n", ans);
        
    }
    
            
    return 0;
}