Can you solve this equation?

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 11155    Accepted Submission(s): 5135

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

 

二分法！

#include<cstdio>
#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
double del(double n)
{
    return 8*pow(n,4)+7*pow(n,3)+2*pow(n,2)+3*n+6;
}
int main()
{
    int t;
    double l,r,mid,y;
    scanf("%d",&t);
    while(t--)
    {
        mid=0;
        scanf("%lf",&y);
        l=0.0;r=100.0;
        if(del(0.0)>y||del(100.0)<y)//如果不在范围内
        {
            cout<<"No solution!"<<endl;
        }
        else
        {
            while(r-l>1e-6)//因为计算机默认精度为10^-6
            {
                mid=(l+r)/2;
                if(del(mid)>y)
                {
                    r=mid;
                }
                else
                {
                    l=mid;
                }
            }
           printf("%.4lf\n",mid);
        }
    }
}