Strange fuction

最新推荐文章于 2024-04-19 20:40:32 发布

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最新推荐文章于 2024-04-19 20:40:32 发布

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Strange fuction

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 4118 Accepted Submission(s): 2960

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

二分法，但是是导函数的二分！注意这一点！

#include<cstdio>
#include<iostream>
#include<cmath>
using namespace std;
double y;
double deal(double n)
{
    return 42*pow(n,6)+48*pow(n,5)+21*pow(n,2)+10*n-y;
}//导函数
int main()
{
    int t;
    double l,r,mid;
    cin>>t;
    while(t--)
    {
        l=0.0;r=100.0;
        cin>>y;
        while(r-l>1e-6)
        {
            mid=(l+r)/2;
            if(deal(mid)<0)
            {
                 l=mid;
            }
            else
            {
                r=mid;
            }
        }//趋向于0导函数值最小！
        printf("%.4lf\n",6*pow(mid,7)+8*pow(mid,6)+7*pow(mid,3)+5*pow(mid,2)-y*mid);
    }
}