hdu 2199 Can you solve this equation?

Can you solve this equation?

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!

解析：二分入门题，可以作为模板。

代码如下：

#include<iostream>#include<cstdio>#include<cmath>using namespace std;double f(double a){    return 8*pow(a,4.0)+7*pow(a,3.0)+2*pow(a,2.0)+3*a+6;   //计算公式}int main(){    double b;    int t;    cin>>t;    while(t--)    {        cin>>b;        double i,j,m,n;        if(f(0)<=b&&f(100)>=b)     //二分条件        {            m=0;            n=100;            while(n-m>1e-6)          //精度取值            {                i=(m+n)/2;            //二分取段                double ans=f(i);     //段位取值                if(ans>b)                   n=i-1e-7;     //如果大于，则把左边的赋值二分位                else                  m=i+1e-7;    //否则把右边的赋值二分位            }            printf("%.4lf\n",(m+n)/2);        }        else          cout<<"No solution!"<<endl;    //否则输出无解    }    return 0;}