CDZSC_2015寒假新人（1）——基础 C

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
struct laoshu
{
    int j;
    int f;
    double s;
};
bool cmp(laoshu stud1,laoshu stud2)
{
    return stud1.s>stud2.s;
}
int main()
{
#ifdef CDZSC_OFFLINE
    freopen("in.txt","r",stdin);
#endif
    int i,m,n;
    double sum;
    laoshu stud[1010];
    while(scanf("%d%d",&m,&n)&&m!=-1&&n!=-1)
    {
        sum=0;
        for(i=0; i<n; i++)
        {
            scanf("%d%d",&stud[i].j,&stud[i].f);
            stud[i].s=1.0*stud[i].j/stud[i].f;
        }
        sort(stud,stud+n,cmp);
        for(i=0; i<n; i++)
        {
            if(m>=stud[i].f)
            {
                sum+=stud[i].j;
                m-=stud[i].f;
            }
            else
            {
                sum+=stud[i].s*m;
                break;
            }
        }
        printf("%.3lf\n",sum);
    }
    return 0;
}