hdu 2199 Can you solve this equation?

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 13292    Accepted Submission(s): 5937

Problem Description

Now,given the equation 8*x^4 + 7*x^3 + 2*x^2 + 3*x + 6 == Y,can you find its solution between 0 and 100;
Now please try your lucky.

 

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 a real number Y (fabs(Y) <= 1e10);

 

Output

For each test case, you should just output one real number(accurate up to 4 decimal places),which is the solution of the equation,or “No solution!”,if there is no solution for the equation between 0 and 100.

 

Sample Input

  
  

   
   2
100
-4
  
  

 

Sample Output

  
  

   
   1.6152
No solution!
  
  
源代码（二分查找）
  
  

   
   
   
   
//1000
#include<stdio.h>
#include<math.h>

double f(double x)
{
    return 8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*x+6;
}

int main()
{
    int t;
    double x1,x2,x3,y,y1,y2,y3;
    scanf("%d",&t);
    while(t--)
    {
        x1=0;
        x2=100;
        scanf("%lf",&y);
        y1=f(x1)-y;
        y2=f(x2)-y;
        if(y1>0||y2<0)
            printf("No solution!\n");
        else
        {
            while(fabs(f(x1)-f(x2))>=0.00001)
            {
                x3=(x1+x2)/2;
                y3=f(x3)-y;
                if(y3>0)
                   x2=x3;
                else
                   x1=x3;
                y1=f(x1)-y;
                y2=f(x2)-y;
            } 
            printf("%.4lf\n",x3);   
        }
        
    }
    return 0;
}