nastya_mod1

#include <utility>
#include <math.h>
#include <iostream>

using namespace std;

double dx = 0.001;

double f(double x)
{
    return pow(x, 2.0 / 3) - x;
}

pair<double, double> F1(double x0, double h)
{
    int k = 1;
    double x1, x2;
    if (f(x0 - h) <= f(x0) && f(x0) <= f(x0 + h))
    {
        x1 = x0 + h;
    }
    else if (f(x0 - h) >= f(x0) && f(x0) >= f(x0 + h))
    {
        x1 = x0 - h;
        h = -h;
    }
    else
    {
        return pair<double, double>((x0 - h < 0) ? 0 : x0 - h, x0 + h);
    }

    x2 = x1;
    x1 = x0;
    do
    {
        x0 = x1;
        x1 = x2;
        x2 = x1 + pow(2.0, k * 1.0) * h;
        k++;
    } while (f(x2) >= f(x1));

    if (h > 0)
    {
        return pair<double, double>(x0 < 0 ? 0 : x0, x2);
    }
    else
    {
        return pair<double, double>(x2 < 0 ? 0 : x2, x0);
    }
}

double fp1(double x)
{
    return (f(x + dx) - f(x)) / dx;
}

double fp2(double x)
{
    return (fp1(x + dx) - fp1(x)) / dx;
}

double F2(pair<double, double> sv, double e)
{
    double x0, x1 = sv.first;
    do
    {
        x0 = x1;
        x1 = x0 - fp1(x0) / fp2(x0);
    } while (abs(x1 - x0) > e);
    return x1;
}

int main()
{
    pair<double, double> a = F1(-100, 0.0001);
    double x = F2(a, 0.001);
    cout << "max = f(" << x << ") = " << f(x) << endl;
    return 0;
}