华为oj之求解立方根

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#include<cstdio>
#include<cmath>
#include<iostream>
using namespace std;

double getCubeRoot(double input)
{
    if(input == 0) return (double)0;
    double pre = 0;
    double res = 1;
    while(abs(res-pre) > 0.000001)
    {
        pre = res;
        res = (2*res + input/(res*res) )/3;   // 迭代公式
    }
    return res;
}

int main()
{
    double in;
    while(cin>>in)
    {
        double res;
        res = getCubeRoot(in);
        printf("%.1f", res);           // 如果需要四舍五入保留1位小数, 最后应该用res+0.05, n位小数则需加5*pow(0.1, n+1)
    }
    return 0;
}