HDUOJ--Strange fuction

Strange fuction

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 2098    Accepted Submission(s): 1577

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

http://acm.hdu.edu.cn/showproblem.php?pid=2899

代码：

 #include<iostream>
 #include<cmath>
 #include<cstdio>
 using namespace std;
 double y;
 double sum(double x)
 {
     return *pow(x,)+*pow(x,)+*pow(x,)+*pow(x,)-y*x;
 }
 double func(double x)
 {
     return *pow(x,)+*pow(x,)+*x*x+*x-y;
 }
 int main()
 {
     int t;
     double mid,left,right;
     cin>>t;
     while(t--)
     {
         scanf("%lf",&y);
         if(func()>)
         {
         left=0.0,right=100.0;
         while(right-left>1e-)
         {
           mid=(right+left)/2.0;
           if(func(mid)>0.0)
                 right=mid;
         else
             if(func(mid)<0.0)
                 left=mid;
             else
                 break;
         }
         printf("%.4lf\n",sum(mid));
         }
         else
             printf("%.4lf\n",sum(100.0));
     }
     return ;
 }