【HDU】2199 - Can you solve this equation?（二分）

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Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others) Total Submission(s): 16459 Accepted Submission(s): 7292

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

注意特判和卡精度就行了。

代码如下：

#include <cstdio>
#include <cmath>
#define f(x) 8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*x+6
int main()
{
	double l,r,mid;
	double y;
	int u;
	scanf ("%d",&u);
	while (u--)
	{
		scanf ("%lf",&y);
		if (y < 6 || y > f(100) + 6)
		{
			printf ("No solution!\n");
			continue;
		}
		l = 0;
		r = 100;
		while (r - l > 1e-8)		//精度卡大一点 
		{
			mid = (r + l) / 2;
			if (f(mid) > y)
				r = mid;
			else
				l = mid;
		}
		printf ("%.4lf\n",l);
	}
	return 0;
}