HD 2199 Can you solve this equation?【二分法求方程的解】

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 13002    Accepted Submission(s): 5823

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!
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AC代码
#include<stdio.h>
#include<math.h>
#include<iostream>
using namespace std;
double Y,l,r,ans,m;
double f(double x)
{
	return 8*pow(x,4) + 7*pow(x,3) + 2*pow(x,2) + 3*pow(x,1) + 6;
}
int main()
{
	int n;
	scanf("%d",&n);
	while(n--)
	{
		scanf("%lf",&Y);
		l=0.0,r=100.0;
        if(Y>=f(0)&&Y<=f(100))
        {
		
		while(r-l>1e-8)//确定精度。 
		{
			m=(r+l)/2;
			ans=f(m);
			if(ans>Y)
			r=m;
			else
			l=m;
		}
	    
		printf("%.4lf\n",(l+r)/2);
	    }
	    else
	    printf("No solution!\n");
	}
	return 0;
}