hdu2199

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 6176    Accepted Submission(s): 2889

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!

 

思路：浮点型的二分法

 

代码：

#include<iostream>
#include<stdio.h>
using namespace std;
double y;
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf",&y);
        if(6<=y&&y<=807020306)
        {
            double m,l,r;
            l=0;
            r=100;
            while(r-l>1e-6)
            {
                m=(l+r)/2;
                if(8*m*m*m*m+7*m*m*m+2*m*m+3*m+6<y)
                    l=m+1e-7;
                else
                    r=m-1e-7;
            }
            printf("%.4lf ",(l+r)/2.0);
        }
        else
            printf("No solution! ");
    }
    return 0;
}