#include<iostream>
using namespace std;
int main() {
double x;
cin>>x;
if(x<0) {
cout<<"-";
x=-x;
}
double l=0,r=x;
while(r-l>1e-8) {
double mid=(l+r)/2;
if(mid*mid*mid>=x) r=mid;
else l=mid;
}
printf("%lf\n",l);
return 0;
}
原文：https://www.cnblogs.com/bingers/p/13223909.html