二分法基础题

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.

InputThe 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);OutputFor 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!

#include<stdio.h>
#include<iostream>  
#include<vector>  
#include <algorithm>
#include<math.h>
  
using namespace std;  
  
double judge(double a)
{
	return 8*pow(a,4.0)+7*pow(a,3.0)+2*a*a+3*a+6;
}
	
int main()  
{
	int cas;
	scanf("%d",&cas);
	while(cas--){
		int Y;
		scanf("%d",&Y);
		double l,r,m;
		if( judge(0) <= Y && Y <= judge(100) ) {  
            l = 0;  
            r = 100;  
            while( r - l > 1e-6 ) {  
                m = (l + r) / 2;   
                double ans = judge(m);  
                if( ans > Y ) {  
                    r = m - 1e-7;  
                }else  
                    l = m + 1e-7;  
            }  
            printf("%.4lf\n", (l + r) / 2 );  
        }else  
            printf("No solution!\n");  
	}
}