HDU 2199 Can you solve this equation?

原题传送门：http://acm.hdu.edu.cn/showproblem.php?pid=2199

 

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 8116    Accepted Submission(s): 3738

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

 

 

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分析：这道题目就是中学里学的二分法求方程的解的问题，注意符合要求的x，f(x) - Y<=0.000001,这个有精确度确定。

//二分法解方程 HDU 2199
#include<cstdio>
#include<cmath>
double low,mid,high;
int Y,t,flag;
using namespace std;
double f(double x){
    double result = 8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*x+6;
    return result;
}
int main(){
    scanf("%d",&t);
    while(t--){
        scanf("%d",&Y);
        low = 0.0;
        high = 100.0;
        flag = 0;
        while(low<high)
        {
            mid = (low+high)/2;
            if(fabs(f(mid)-Y)<= 0.000001)
            {
                flag = 1;
                break;
            }else if(f(mid)-Y>0)
            {
                high = mid;
            }else
            {
                low = mid;
            }
        }
        if(flag){
            printf("%.4f\n",mid);
        }else{
            printf("%s\n","No solution!");
        }
    }


}