hdu 2899 三分查找求极值

#include <iostream>
#include <cmath>
#include <stdio.h>
using namespace std;

#define eps 1e-6

double f(double x,double y)
{
    return 6.0*pow(x,7.0)+8.0*pow(x,6.0)+7.0*pow(x,3.0)+5.0*pow(x,2.0)-y*x;
}

int main()
{
    int t,tt;
    double sum,mid,tmid,l,r,y;
    freopen("in.txt","r",stdin);
    scanf("%d",&t);
    for(tt=1;tt<=t;tt++)
    {
        scanf("%lf",&y);
        l=0;r=100;
        while((r-l)>eps)
        {
            mid=(l+r)/2;
            tmid=(mid+r)/2;
            if(f(mid,y)<f(tmid,y))
            r=tmid;
            else
            l=mid;
        }
        printf("%.4lf\n",f(mid,y));
    }
    return 0;
}