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[];

 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 == - && n == -)
             break;

         for(int i = ; 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 = ;
         for(int i = ; 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 ;
 }