c-二分

C - 二分

Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u

Submit  Status  Practice  HDU 2199

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!
        
        
       
       

 

二分法

代码：

#include<stdio.h>

double sz(double n)
{
	return 8 * n * n * n * n + 2 * n * n + 7 * n * n * n + 3 * n + 6;
}

int main()
{
	int t;
	scanf_s("%d", &t);
	while (t--)
	{
		double y;
		scanf_s("%lf", &y);
		if (sz(0) > y || sz(100) < y)
		{
			printf("No solution!\n");
			continue;
		}
		double l = 0, r = 100, mid;
		while (r - l>1e-10)
		{
			mid = (r + l) / 2;
			if (sz(mid) > y)
			{
				r = mid;
			}
			else
			{
				l = mid;
			}
		}
		printf("%.4lf\n", mid);
	}

	return 0;
}