#include <iostream>
#include <cmath>

using namespace std;

double f(double x)
{
    return -3 * x / (pow(x, 2) + 1);
}

int min(double* x)
{
    if (f(x[0]) < min(f(x[1]), f(x[2])))
    {
        return 0;
    }

    if (f(x[1]) < min(f(x[0]), f(x[2])))
    {
        return 1;
    }

    return 2;
}

int max(double* x, double x_ser)
{
    if (f(x[0]) > max(f(x[1]), max(f(x[2]), f(x_ser))))
    {
        return 0;
    }

    if (f(x[1]) > max(f(x[0]), max(f(x[2]), f(x_ser))))
    {
        return 1;
    }

    if (f(x[2]) > max(f(x[1]), max(f(x[0]), f(x_ser))))
    {
        return 2;
    }

    return 3;
}

double* sort_x(double* x)
{
    for (int i = 0; i < 2; i++)
    {
        if (x[0] > x[1])
        {
            swap(x[0], x[1]);
        }

        if (x[1] > x[2])
        {
            swap(x[1], x[2]);
        }
    }

    return x;
}

double* calc_x(double* x, double x_ser)
{
    int i_max = max(x, x_ser);

    if (i_max != 3)
    {
        x[i_max] = x_ser;
    }

    return sort_x(x);
}

double calc(double h, double a, double b, double eps_x, double eps_y)
{
    int i = 0;
    double* x = new double[3], x_ser, x_prec = 500, y_prec = 500, x_min, f_min, x_prec_p, y_prec_p ;

    x[0] = (b - a) / 4;
    x[1] = x[0] + h;

    if (f(x[1]) > f(x[0]))
    {
        x[2] = x[0] - h;
    }
    else
    {
        x[2] = x[0] + 2 * h;
    }

    while (true)
    {
        x_ser = 0.5 * ((f(x[0]) * (pow(x[1], 2) - pow(x[2], 2)) + f(x[1]) * (pow(x[2], 2) - pow(x[0], 2)) + f(x[2]) * (pow(x[0], 2) - pow(x[1], 2))) / ((f(x[0]) * (x[1] - x[2]) + f(x[1]) * (x[2] - x[0]) + f(x[2]) * (x[0] - x[1]))));

        x_min = x[min(x)];
        f_min = f(x_min);

        x_prec_p = x_prec;
        y_prec_p = y_prec;

        x_prec = fabs((x_min - x_ser) / x_ser);
        y_prec = fabs((f_min - f(x_ser)) / f(x_ser));

        cout << "x1 = " << x[0] << " x2 = " << x[1] << " x3 = " << x[2] << " h = " << h << endl;
        cout << "x_prec = " << x_prec << " y_prec = " << y_prec << endl << endl;

        if (eps_x > x_prec && eps_y > y_prec)
        {
            break;
        }

        if (fabs(x_prec - x_prec_p) < 1e-2 && fabs(y_prec - y_prec_p) < 1e-2)
        {
            return calc(h / 2, a, b, eps_x, eps_y);
        }

        i++;

        if (i > 10) {
            return 0;
        }

        x = calc_x(x, x_ser);
    }

    return f_min > f(x_ser) ? x_ser : x_min;
}

int main()
{
    double xsr, a, b, eps_x, eps_y, h, x_min;

    h = 1;
    a = 0;
    b = 5;
    eps_x = 0.03;
    eps_y = 0.003;

    x_min = calc(h, a, b, eps_x, eps_y);

    cout << "x_min = " << x_min << endl;
    cout << "f_min = " << f(x_min) << endl;
}