hdu 1.3.1 FatMouse' Trade

贪心的运用，主要看其比值，取最大值实现贪心...

#include<cstdio>
#include<algorithm>
#include<vector>
using namespace std;

struct room
{
    int j;
    int f;
    bool operator < (const room t)const
    {
        return (float)j/f >(float)t.j/t.f;
    }
};

int main()
{
    //freopen("input.txt","r",stdin);
    int m,n,i;
    double ans;
    while(scanf("%d%d",&m,&n) && (m+1) &&(n+1))
    {
        vector<room> v;
        room r;
        ans = 0;
        for(i = 0; i < n; i++)
        {
            scanf("%d%d",&r.j,&r.f);
            v.push_back(r);
        }
        sort(v.begin(),v.end());

        i = 0;
        while(m > 0 && i < v.size())
        {
            if(v[i].f <= m)
            {
                m -= v[i].f;
                ans += v[i].j;
            }
            else
            {
                ans += (double)(v[i].j* m)/v[i].f ;
                m = 0;//½áÊø
            }
            i++;
        }
        printf("%.3lf
",ans);
    }

    return 0;
}