贪心算法 hdu 1009

#include<iostream>
#include<algorithm>
using namespace std;
struct warehouse{
    double j,f,p;
};
warehouse ware[1005];
bool cmp(warehouse a,warehouse b)
{
    if(a.p>=b.p)return true;
    else return false;
}
int main()
{
     int m,n;
     double sum;
     while(cin>>m>>n)
     {
         sum=0;
         if(m==-1&&n==-1)
            break;
         for(int i=0;i<n;i++)
         {
             cin>>ware[i].j>>ware[i].f;
             ware[i].p=ware[i].j/ware[i].f;
         }
         sort(ware,ware+n,cmp);
         for(int i=0;i<n&&m;i++)
         {
             if(m>ware[i].f)
                {
                    m=m-ware[i].f;
                    sum=sum+ware[i].j;
                }
             else
                {

                    sum+=(m*1.0/ware[i].f)*ware[i].j;
                    m=0;
                }
         }
         printf("%.3f\n",sum);
     }
    return 0;
}