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

Author

Redow

二分，很简单。

#include<iostream>
#include<stdio.h>
#include<math.h>
using namespace std;
double y;
double A(double x)
{
    return 42*pow(x,6)+48*pow(x,5)+21*pow(x,2)+10*x;
}
int main()
{

    int T;
    cin>>T;

    while(T--)
    {
        double low=0.0;
        double high=100.0;
        double mid;
        cin>>y;
        if(A(100)<y)
        {
            printf("%.4lf",6*pow(100,7)+8*pow(100,6)+7*pow(100,3)+5*pow(100,2)-y*100);
            continue;
        }

        while(low+1e-8<high)
        {
            mid=(low+high)/2.0;

            if(A(mid)>y)
                high=mid;
            else
                low=mid;
        }

        printf("%.4lf\n",6*pow(low,7)+8*pow(low,6)+7*pow(low,3)+5*pow(low,2)-y*low);
    }
    return 0;
}