[AcWing 790] 数的三次方根

#include<iostream>

using namespace std;

int main()
{
    double x;
    scanf("%lf", &x);
    double l = -1e5, r = 1e5;
    while (r - l > 1e-8) {
        double mid = (l + r) / 2;
        if (x <= mid * mid * mid)   r = mid;
        else    l = mid;
    }
    printf("%.6f", l);
    return 0;
}