hdu 2899 Strange fuction

Strange fuction

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 2077    Accepted Submission(s): 1556

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

 二分练手题

#include<stdio.h>
#include<math.h>
double y;
double solve(double x)
{
     double n;
     n=42*pow(x,6)+ 48*pow(x,5) + 21*x*x + 10*x ;
     return n;
}
int main()
{
     int t;
     double y,l,r,p,mid,x;
     scanf("%d",&t);
     while(t--)
     {
          scanf("%lf",&y);
       //  if(solve(100)<y)//貌似没有这种情况
          //{
            //   x=100;
             //  printf("%.4lf
",6 * pow(x,7)+8*pow(x,6)+7*x*x*x+5*x*x-y*x);
             //  continue;
         // }
          l=0.0,r=100.0;
          while(r-l>1e-9)
          {
               mid=(r+l)/2;
               p=solve(mid);
               if(p<y)
               l=mid;
               else
               r=mid;

          }
          x=mid;
          p= 6 * pow(x,7)+8*pow(x,6)+7*x*x*x+5*x*x-y*x ;
          printf("%.4lf
",p);
     }
     return 0;
}