connect4.rb

class Board
    def initialize()
        # 7 columns
        @board = Array.new(7)

        # 6 rows per column
        for x in 0..6
            @board[x] = Array.new(6)
            for y in 0..5
                @board[x][y] = 0
            end
        end
    end

    def draw
        for y in 0..5
            reverse_y = 5 - y
            print reverse_y, " |"
            for x in 0..6
                print " ", @board[x][reverse_y]
            end
            # print special "newline" character
            print "\n" 
        end

        print "  +"
        for x in 0..6
            print "--"
        end
        print "-\n"

        print "   "
        for x in 0..6
            print " ", x
        end
        print "\n\n" 
    end

    def column_height(column)
        # check column height
        for y in 0..5
            if (@board[column][y] == 0)
                return y
            end
        end
        
        return 6
    end
    
    def do_move(player_id, column)
        height = column_height(column)

        # make move if possible
        if (height < 6)
            @board[column][height] = player_id
            success = true
        else
            success = false
        end

        return success
    end
    
    def undo_move(player_id, column)
        height = column_height(column)
        
        if (height > 0)
            if (@board[column][height - 1] == player_id)
                @board[column][height - 1] = 0
            else
                raise Exception.new("Trying to remove stone with incorrect player id.")
            end
        else
            raise Exception.new("Trying to remove stone from empty column.")
        end
    end
end

board = Board.new()
player = 2
while (Board.game_over?(player))
    if (player == 1)
        player = 2
    else
        player = 1
    end

    board.draw()

    if (player == 1)
        # human player
        success = false
        while not success
            print "Where do you want to move (enter a column number 0-6): "
            column = gets.to_i()
            success = board.do_move(player, column)
            if not success
                print "It's illegal to move in column ", column, ".\n"
            end
        end
    else
        # random computer player
        success = false
        while not success
            column = rand(7)
            success = board.do_move(player, column)
        end
    end
        
    print "\n"
end