Task: 21 game


C++: 

#include <cstdlib>
#include <ctime>
#include <iostream>
#include <iomanip>
#include <limits>

using namespace std;
#define _(STR) STR


class Model
{
public:
    static const int GOAL = 21;
    static const int NUMBER_OF_PLAYERS = 2;
    static const int MIN_MOVE = 1;
    static const int MAX_MOVE = 3;
    int bestMove();
    bool update(const char* player, int move);
    bool isGameBegin();
    bool isGameOver();
protected:
    friend class View;
    View* view = nullptr;
    const char* player = nullptr;
    int oldTotal = 0;
    int newTotal = 0;
    int lastMove = 0;
};


class View
{
protected:
    Model* model;
public:
    View(Model* model);
    void init(const char* player);
    void update();
};


class Controller
{
protected:
    Model* model;
    View* view;
public:
    Controller(Model* model, View* view);
    int input();
    void clear();
    void run();
};


int Model::bestMove()
{
    
    

    int move = MIN_MOVE;
    for (int i = MIN_MOVE; i <= MAX_MOVE; i++)
        if ((newTotal + i - 1) % (MAX_MOVE + 1) == 0)
            move = i;
    for (int i = MIN_MOVE; i <= MAX_MOVE; i++)
        if (newTotal + i == GOAL)
            move = i;
    return move;
}

bool Model::update(const char* player, int move)
{
    if (move >= MIN_MOVE && move <= MAX_MOVE && newTotal + move <= GOAL)
    {
        this->player = player;
        oldTotal = newTotal;
        newTotal = oldTotal + move;
        lastMove = move;
        view->update();
        return true;
    }
    else
        return false;
}

bool Model::isGameBegin()
{
    return oldTotal == 0;
}

bool Model::isGameOver()
{
    return newTotal == GOAL;
}


View::View(Model* model)
{
    this->model = model;
    model->view = this;
}

void View::init(const char* player)
{
    if (model->newTotal == 0)
        cout << _("----NEW GAME----\n\n")
             << _("The running total is currently zero.\n")
             << _("The first move is ") << player << _(" move.\n\n");
}

void View::update()
{
    cout << setw(8) << model->player << ": " << model->newTotal << " = "
         << model->oldTotal << " + " << model->lastMove << endl << endl;
    if (model->isGameOver())
        cout << endl << _("The winner is ") << model->player << _(".\n\n\n");
}


Controller::Controller(Model* model, View* view)
{
    this->model = model;
    this->view = view;
}

void Controller::run()
{
    if (rand() % Model::NUMBER_OF_PLAYERS == 0)
    {
        view->init("AI");
        model->update("AI", model->bestMove());
    }
    else
        view->init("human");

    while (!model->isGameOver())
    {
        while (!model->update("human", input()))
            clear();
        model->update("AI", model->bestMove());
    }
}

int Controller::input()
{
    int value;
    cout << _("enter a valid number to play (or enter 0 to exit game): ");
    cin >> value;
    cout << endl;
    if (!cin.fail())
    {
        if (value == 0)
            exit(EXIT_SUCCESS);
        else
            return value;
    }
    else
        return model->MIN_MOVE - 1;
}

void Controller::clear()
{
    cout << _("Your answer is not a valid choice.") << endl;
    cin.clear();
    cin.ignore((streamsize)numeric_limits<int>::max, '\n');
}


int main(int argc, char* argv)
{
    srand(time(NULL));

    cout << _(
        "21 Game                                                          \n"
        "                                                                 \n"
        "21 is a two player game, the game is played by choosing a number \n"
        "(1, 2, or 3) to be added to the running total. The game is won by\n"
        "the player whose chosen number causes the running total to reach \n"
        "exactly 21. The running total starts at zero.                    \n\n");

    while (true)
    {
        Model* model = new Model();
        View* view = new View(model);
        Controller* controler = new  Controller(model, view);

        controler->run();

        delete controler;
        delete model;
        delete view;
    }
    return EXIT_SUCCESS; 
}









Fortran: 

subroutine ai
  common itotal, igoal
  if (itotal .lt. igoal) then
    move = 1
    do i = 1, 3
      if (mod(itotal + i - 1 , 4) .eq. 0) then
        move = i
      end if
    end do
    do i = 1, 3
      if (itotal + i .eq. igoal) then
        move = i
      end if
    end do
    print *, "      ai  ", itotal + move, " = ", itotal, " + ", move
    itotal = itotal + move
    if (itotal .eq. igoal) then
      print *, ""
      print *, "the winner is ai"
      print *, ""
    end if
  end if
end subroutine ai

subroutine human
  common itotal, igoal
  print *, ""
  do while (.true.)
    if (itotal + 1 .eq. igoal) then
      print *, "enter 1 (or 0 to exit): "
    else if (itotal + 2 .eq. igoal) then
      print *, "enter 1 or 2 (or 0 to exit): "
    else
      print *, "enter 1 or 2 or 3 (or 0 to exit)"
    end if
    read(*,*) move
    if (move .eq. 0) then
      stop
    else if (move .ge. 1 .and. move .le. 3 .and. move + itotal .le. igoal) then
      print *, "   human  ", itotal + move, " = ", itotal, " + ", move
      itotal = itotal + move
      if (itotal .eq. igoal) then
        print *, ""
        print *, "the winner is human"
        print *, ""
      end if
      return
    else
      print *, "a bad choice"
    end if
  end do
end subroutine human

program main
  common itotal, igoal
  print *,"game 21 - an example in fortran iv language for rosseta code."
  print *,""
  print *,"21 is a two player game, the game is played by choosing a number"
  print *,"(1, 2, or 3) to be added to the running total. the game is won"
  print *,"by the player whose chosen number causes the running total to reach"
  print *,"exactly 21. the running total starts at zero."
  print *,""
  i = irand(1)
  igoal = 21
  do while(.true.)
    print *, "---- new game ----"
    print *, ""
    print *, "the running total is currently zero."
    print *, ""
    itotal = 0
    if (mod(irand(0), 2) .eq. 0) then
      print *, "the first move is ai move."
      call ai
    else
      print *, "the first move is human move."
    end if
    print *, ""
    do while(itotal .lt. igoal)
      call human
      call ai
    end do
end do
end program main