HDOJ2199Can you solve this equation?（二分）

Can you solve this equation?

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

Total Submission(s): 14379    Accepted Submission(s): 6421

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!

Author

Redow

注意精度即可。

#include<stdio.h>
#include<math.h> 
double fx(double x)
{
  return 8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*x+6;
} 
int main()
{
  int test;
  double k,j,y;
  scanf("%d",&test);
  while(test--)
  {
    scanf("%lf",&y);
    if(y>=fx(0)&&y<=fx(100))
    {
      k=0;
      j=100;
      while(j-k>=1e-7)
      {
        if(fx((k+j)/2)<y)
          k=(k+j)/2;
        else
            j=(k+j)/2;
      }
      printf("%.4lf\n",(j+k)/2);
    }
    else
    printf("No solution!\n");
  }
  
}