HDU 2899 Strange fuction

Strange fuction

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Problem Description

Now, here is a fuction:
  F(x) = 6 * x^7+8*x^6+7*x^3+5*x^2-y*x (0 <= x <=100)
Can you find the minimum value when x is between 0 and 100.

 

Input

The first line of the input contains an integer T(1<=T<=100) which means the number of test cases. Then T lines follow, each line has only one real numbers Y.(0 < Y <1e10)

 

Output

Just the minimum value (accurate up to 4 decimal places),when x is between 0 and 100.

 

Sample Input

2
100
200

 

Sample Output

-74.4291
-178.8534

 

#include<stdio.h>
#include<iostream>
#include<math.h>
using namespace std;
double f(double x,double y)
{
        return 6*pow(x,7)+8*pow(x,6)+7*pow(x,3)+5*x*x-y*x;
}
int main()
{
        int t;
        scanf("%d",&t);
        while(t--)
        {
                double y;
                scanf("%lf",&y);
                double a,b,c;
                double mid,midmid,left=0.0,right=100.0;
                while(right-left>1e-6)
                {
                        mid=(left+right)/2.0;
                        midmid=(mid+right)/2.0;
                        a=f(mid,y);
                        b=f(midmid,y);
                        if(a>b)
                        {
                                left=mid;
                        }
                        else
                        {
                                right=midmid;
                        }
                }
                c=f((left+right)/2.0,y);
                printf("%.4f\n",c);
        }
	return 0;
}