hdu 2199 Can you solve this equation? 二分

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 6763    Accepted Submission(s): 3154

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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/*
对于精度，我表示囧。
我以为，保留4位小数，就到1e-5就可以了。

*/

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<cstdlib>
#include<math.h>
using namespace std;

double fun(double x)
{
    return 8*x*x*x*x+7*x*x*x+2*x*x+3*x+6;
}
void EF(double l,double r,double Y)
{
    double mid;
    while(r-l>1e-7)
    {
        mid=(l+r)/2;
        double ans=fun(mid);
        if( ans >Y )
            r=mid-1e-8;
        else l=mid+1e-8;
    }
    printf("%.4lf\n",(l+r)/2);
}
int main()
{
    int T;
    double Y;
    scanf("%d",&T);
    {
        while(T--)
        {
            scanf("%lf",&Y);
            if( fun(0.0)>Y || fun(100.0)<Y)
                printf("No solution!\n");
            else
                 EF(0.0,100.0,Y);
        }
    }
    return 0;
}