求立方根

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;
double Lifanggen(double src)
{
	double curx,nextx;
	double fenzi,fenmu;
	const double  precision = 0.1; /* 精度 */
	int flag = 0;
	curx = src;
	
	if (src == 0)
	{
		return 0;
	}
	fenzi = curx*curx*curx-src;
	fenmu = 3*curx*curx;
	do
	{
		nextx = curx-fenzi/fenmu;       /* 牛顿迭代公式 */
		if (fabs(curx-nextx) <= precision)
		{
			flag = 1;
		}   
		else
		{
			flag = 0;
			curx = nextx;
		}
		fenzi = curx*curx*curx-src;
		fenmu = 3*curx*curx;
     }while(flag == 0);
	
	return nextx;
}
int main()
{
//	fstream in("data.txt");
	double src,dst;
	
	cin>>src;
	dst = Lifanggen(src);
	printf("%.1f",dst);
	cout<<endl;
	return 0;
}