杭电 HDU 2199

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 19266 Accepted Submission(s): 8484

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!

#include<cstdio>
#include<math.h>

double h(double x)
{
    return 8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*x+6;
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        double y;
        scanf("%lf",&y);
        if(y>=h(0)&&y<=h(100))   /// 保证y值的范围
        {
            double l=0;         ///二分思想
            double r=100;
            while(r-l>1e-7)  ///注意精度
            {
                double m=(l+r)/2.0;
                if(h(m)<y)
                {
                    l=m+1e-8;
                }
                else
                {
                    r=m-1e-8;
                }

            }printf("%.4lf\n",(l+r)/2.0);
        }
        else
            printf("No solution!\n");

    }
}