Strange fuction

Strange fuction

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

Total Submission(s): 661 Accepted Submission(s): 544

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

 

Recommend

lcy

 

/*
拐了点小弯，最小值点就是导数为零的点
*/
#include<bits/stdc++.h>
#define op 1e-8
using namespace std;
double F(double x,double y)
{
    return 6*x*x*x*x*x*x*x+8*x*x*x*x*x*x+7*x*x*x+5*x*x-y*x;
}
double derivative_F(double x,double y)
{
    return 42*x*x*x*x*x*x+48*x*x*x*x*x+21*x*x+10*x-y;
}
int main()
{
    //freopen("C:\\Users\\acer\\Desktop\\in.txt","r",stdin);
    int t;
    double y;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf",&y);
        double l=0,r=100,mid;
        while(fabs(r-l)>op)
        {
            mid=(r+l)*1.0/2;
            if(derivative_F(mid,y)>0)
                r=mid;
            else
                l=mid;
        }
        printf("%.4lf\n",F(l,y));
    }
    return 0;
}