hdu 2199 二分搜索

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 19647    Accepted Submission(s): 8664

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!

 

注意控制精度，不然会超时，虽然是保留四位小数，但是精度得10的-8次方左右

#include<iostream>
#include<stdio.h>
#define exp 1e-8
using namespace std;

double key;

double Binary(double low,double high)
{
    while(high-low>exp)
    {
        double mid = (low+high)/2;
        if(8*mid*mid*mid*mid + 7*mid*mid*mid + 2*mid*mid + 3*mid + 6 > key)
            high=mid-exp;
        else
            low=mid+exp;
    }
    return low;
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf",&key);
        if(6>key || 8*100*100*100*100 + 7*100*100*100 + 2*100*100 + 3*100 + 6 < key)
            printf("No solution!\n");
        else
            printf("%.4f\n",Binary(0, 100));
    }
    return 0;
}