tambola-ticket-generator.rb

=begin
  expected output is a 2d array
  irb(main):001:0> TicketGenerator.new.generate
  => [[nil, 10, 27, 31, 45, 54, 60, nil, nil], [nil, nil, 29, 32, nil, 58, 61, 77, nil], [5, 11, nil, nil, nil, nil, 64, nil, 88]]
  irb(main):002:0> TicketGenerator.new.generate
  => [[2, nil, nil, nil, nil, 51, 68, 71, 82], [nil, 19, 23, 34, 45, 57, 69, 73, nil], [nil, nil, nil, 35, nil, nil, nil, 75, 83]]
  irb(main):003:0> 
=end


class TicketGenerator
  def initialize
    @shell = create_shell
  end

  def generate
    generate_pattern
  end

  def flat
    @shell.flatten.compact.sort
  end

  def to_s
    @shell.each do |row|
      row.each do |col|
        print(("%02d" % col.to_i).ljust(3))
      end
      print "\n"
    end
  end

  private

  # this is the core logic of generating a tambola ticket
  # it has 3 rows x 9 columns = 27 cells
  # the ticket should have exactly 15 numbers values
  # the number ranges from 1..90
  # column 1 can have number from 1 - 9
  # column 2 can have numbers from 10 - 19 and so on
  # column 9 can have numbers from 80 - 90
  # each column must have at least one number
  # each column can have one, two or three numbers
  # each row can have max 5 numbers
  def generate_pattern
    @cells_to_fill = 15
    @ticket_capacity_left = Array.new(9) { 3 }
    @exhaustive = Array(1..90)

    # fill in a number for each column
    fill_shell([1, 2, 3, 4, 5, 6, 7, 8, 9, 10].sample)
    fill_shell([11, 12, 13, 14, 15, 16, 17, 18, 19, 20].sample)
    fill_shell([21, 22, 23, 24, 25, 26, 27, 28, 29, 30].sample)
    fill_shell([31, 32, 33, 34, 35, 36, 37, 38, 39, 40].sample)
    fill_shell([41, 42, 43, 44, 45, 46, 47, 48, 49, 50].sample)
    fill_shell([51, 52, 53, 54, 55, 56, 57, 58, 59, 60].sample)
    fill_shell([61, 62, 63, 64, 65, 66, 67, 68, 69, 70].sample)
    fill_shell([71, 72, 73, 74, 75, 76, 77, 78, 79, 80].sample)
    fill_shell([81, 82, 83, 84, 85, 86, 87, 88, 89, 90].sample)

    loop do
      fill_shell(@exhaustive.sample)
      break if @cells_to_fill == 0
    end

    # sort values in right order
    @shell.each(&:sort!)

    # fill up with right nil values
    @shell = @shell.map do |col|
      filled_probability = Array.new(col.size) { 1 }
      empty_probability = Array.new(3 - col.size) { 0 }
      order_by_probability = (filled_probability + empty_probability).shuffle
      temp_col = []
      order_by_probability.each do |p|
        temp_col.push(nil) if p == 0
        temp_col.push(col.delete_at(0)) if p == 1
      end
      temp_col
    end

    # remove unwanted instantce variables
    clean_up

    # transpose the values
    @shell = @shell.transpose
  end

  # push the value in the right column
  # removes the number from exhaustive list
  # decrement the cells to fill counter
  def fill_shell(value)
    col = value.to_i / 10
    # handle the special case of 90
    col = 8 if value == 90
    return if @ticket_capacity_left[col] == 0

    @shell[col].push(value)
    @exhaustive.delete(value);
    @cells_to_fill -= 1
    @ticket_capacity_left[col] -= 1
  end

  def create_shell
    Array.new(9) { Array.new() }
  end

  def clean_up
    remove_instance_variable(:@ticket_capacity_left)
    remove_instance_variable(:@cells_to_fill)
    remove_instance_variable(:@exhaustive)
  end
end