hdu2199_Can you solve this equation?

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

2100-4 

 

Sample Output

1.6152No solution!                

 

这个题二分比较明显，但是二分法要注意返回的值，返回不同的值有精度问题。

#include <stdio.h>

#include <math.h>


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


double bs(double low,double high,double y)
{
    double mid;
    while(high-low>1e-7)
    {
        mid=(high+low)/2;
        if(an(mid) > y) high=mid;
        else low=mid;
    }
    return high;
}


int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        double y;
        scanf("%lf",&y);
        if(y<an(0)||y>an(100.0))
           printf("No solution!\n");
        else
           printf("%.4lf\n",bs(0,100,y));
    }
    return 0;
}