计算一个数字的立方根，不使用库函数

#include <iostream>

#include<iomanip>

#define E 0.0001 //精度设置

using namespace std;

double getCubeRoot(double num)

{

double x0=num;

double result;

while (1)

{

result=x0-(x0*x0*x0-num)/(3*x0*x0); //牛顿迭代 f(x) = x^3-num, f'(x)=3*x^2;x=x-f(x)/f'(x);

if (result*result*result-num<E &&result*result*result-num>-E)

return result;

else

x0=result;

}

}

int main()

{

int number;

cin>>number;

cout<< fixed << showpoint << setprecision(1)<<getCubeRoot(number)<<endl;

}