#pragma once
#include <stdio.h>

double func(double t, double y) {
        return 2 * t*y;
}


double* modifiedEylersMethod(double begin_t, double begin_y, double h, double end_t)
{
        int countStep = (end_t - begin_t) / h;
        double* container = new double[countStep];
        double previous_func = func(begin_t, begin_y);
        double current_t = begin_t;
        container[0] = begin_y;
        for (int i = 1; i <= countStep; begin_t += h, i++)
        {               // = begin_y + (h / 2)*(2 * begin_t*begin_y + ((2 * begin_t + h)*(begin_y + h * 2 * begin_t*begin_y)));
                container[i] = container[i - 1] + h*func(current_t + h / 2, container[i - 1] + h / 2 * previous_func);
                current_t += h,
                previous_func = func(current_t, container[i]);
        }
        return container;

}


double* simpleEyler(double begin_t, double begin_y, double h, double end_t) {


        int countStep = (end_t - begin_t) / h;
        double* container = new double[countStep];
        double previous_func = func(begin_t, begin_y);
        container[0] = begin_y;
        double current_t = begin_t + h;
        for (int i = 1; i <= countStep; i++) {
                container[i] = container[i-1] + h * previous_func;
                current_t += h;
                previous_func = func(current_t,container[i]);
        }
        return container;
}

double* rungekutt(double begin_t, double begin_y, double h, double end_t) {

        int countStep = (end_t - begin_t) / h;

        double* container = new double[countStep];
        container[0] = begin_y;
        double current_t = begin_t;

        for (int i = 1; i <= countStep; i++) {
                double current_y = container[i - 1];
                double k1 = func(current_t, current_y);
                double k2 = func(current_t + (h / 2), current_y + (h / 2)*k1);
                double k3 = func(current_t + (h / 2), current_y + (h / 2)*k2);
                double k4 = func(current_t + h, current_y + h * k3);
                double k = k1 + 2 * k2 + 2 * k3 + k4;
                container[i] = current_y + (h*k / 6);
                current_t += h;
        }

        return container;

}