hdu 2199 二分法求方程的根

D - Can you solve this equation?
Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d
& %I64u
Submit Status

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!
思路：没什么好说的,直接开精度二分暴力,注意没有解得条件
#include<stdio.h>
#include<math.h>
#define e 0.00000001
#define g(x) 8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*x+6//直接定义define即可;
double y;
int main()
{   int t;
    double l,mid,r;
    scanf("%d",&t);
    while(t--)
    {   
  scanf("%lf",&y);
 if(y<g(0)||y>g(100))
 {   printf("No solution!\n");
     continue;
 }
 l=0;
  r=100;
      while(r-l>e)
      {    mid=(l+r)/2;
          if(g(mid)>y)
              r=mid;
  else
       l=mid;
  
 }
      printf("%.4lf\n",l);
}
return 0;
}
可能有些人不理解二分,我们这里所求的二分默认只能求出有解的那种情况,不需要去判断是否有根