hdu 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): 412    Accepted Submission(s): 237

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

 

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lcy

分析：典型二分，注意eps取值要恰当

#include<cmath>
#include<cstdio>
#define eps 1e-8
double fun(double x)
{
    return 8*x*x*x*x + 7*x*x*x + 2*x*x + 3*x + 6;
}
int main()
{
    double y,a,b,m,d;
    int T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%lf",&y);
        if(y<6 || y>807020306)
        {
            printf("No solution!\n");
            continue;
        }
        a=0.0;
        b=100.0;
        while(b-a>eps)
        {
            m=(a+b)/2;
            if(fun(m)<y)
                            a=m;
                        else
                            b=m;
        }
        printf("%.4f\n",a);
    }
    return 0;
}