g++ -c *.cpp && g++ *.o && ./a.out

main.cpp

#include "point.h"
#include <iostream>

using namespace std;

int main(){
    Point2D p1 = Point2D(10, 20);
    cout << "Координаты точки p1: ";
    p1.print_coordinates();

    Point2D p2 = Point2D(30, 40);
    cout << "Координаты точки p2: ";
    p2.print_coordinates();

    Point2D result = Point2D(0, 0);

    result = p1 + p2;
    cout << "Сумма точек p1 и p2: ";
    result.print_coordinates(); // 40|60

    result = p1 - p2;
    cout << "Разница точек p1 и p2: ";
    result.print_coordinates(); // 70|100

    cout << "Дружественная функция класса Point2D: " << endl;
    cout << p2.get_rand() << endl;

    // for(int i=0; i<20; i++){
    //     Point3D p = Point3D(10, 10, 2);
    //     cout << p.get_count() << endl;
    // }

    return 0;
}

point.cpp

#include "point.h"
#include <iostream>
#include <stdlib.h>

using namespace std;

int Point::get_rand(){
    return rand() % 10;
}

Point2D::Point2D(int i1, int i2): Point() {
    count += 1;
    x = i1;
    y = i2;
}

int Point2D::get_count(){
    return count;
}

void Point2D::set_x(int new_x){
    x = new_x;
}

void Point2D::set_y(int new_y){
    y = new_y;
}

void Point2D::print_coordinates(){
    cout << x << "|" << y << endl;
}

void Point3D::print_coordinates(){
    cout << x << "|" << y << endl;
}

Point2D Point2D::operator+(Point2D& other){
    Point2D p = Point2D(x + other.x, y + other.y);
    return p;
}

Point2D Point2D::operator-(Point2D& other){
    Point2D p = Point2D(x - other.x, y - other.y);
    return p;
}

Point3D::Point3D(int i1, int i2, int i3): Point2D(0,0) {
    count += 1;
    x = i1;
    y = i2;
    z = i3;
}

point.h

class Count {
public:
    int count;
    virtual int get_count() =0;
};

class Point {
public:
    virtual void print_coordinates() =0;
    int get_rand();
};

class Point2D : public Point, public Count {
public:
    Point2D(int, int);
    void set_x(int);
    void set_y(int);
    void print_coordinates();
    int get_count();

    friend int Point::get_rand();
    
    Point2D operator+(Point2D&);
    Point2D operator-(Point2D&);
protected:
    int x;
    int y;
};

class Point3D : public Point2D {
public:
    Point3D(int, int, int);
    void set_z(int);
    void print_coordinates();

    friend int Point::get_rand();

    Point3D operator+(Point3D&);
    Point3D operator-(Point3D&);
protected:
    int z;
};