Determining a poker hand with two arrays

Question

I want to create a simple multiplayer poker program in ruby, but I feel like I'm reinventing the wheel:

table = [card1, card2, card3, card4, card5]
mike = [card6, card7]
john = [card8, card9]

card6.face = "A"
card6.suit = "spades"

I'm having a hard time writing an algorithm to decide which of the possible hands each player has.

For example, in order to determine if a player was dealt a flush I wrote something like this:

  together = table + hand

  # Populate hash with number of times each suit was found
  $suits.each do |suit|
    matched[suit] = together.select{|card| card.suit == suit}.size
  end
  matched.each do |k,v|
    if v == 5
      puts "#{k} were seen five times, looks like a flush."
    end
  end

This doesn't seem very comprehensive (No way to tell if it's an Ace-high or a 6-high flush) nor very ruby-like.

Is there a more obvious way to determine hands in poker?

You can have a look at this gem: https://github.com/robolson/ruby-poker — siekfried, Feb 21 '14 at 08:26

aherve · Accepted Answer · 2014-02-21T11:02:57.630

It's probably far from perfect, but I wrote some methods to detect poker hands to solve a project euler problem. Maybe it can give you some ideas ; full code is here: https://github.com/aherve/Euler/blob/master/pb54.rb

In a nutshell, Hand is defined by an array of Card, that respond to Card.value and Card.type:

  def royal_flush?
    return @cards if straight_flush? and @cards.map(&:value).max == Poker::values.max
  end

  def straight_flush?
    return @cards if straight? and @cards.map(&:type).uniq.size == 1
  end

  def four_of_a_kind?
    x_of_a_kind?(4)
  end

  def full_house?
    return @hand if three_of_a_kind? and Hand.new(@cards - three_of_a_kind?).one_pair?
    return nil
  end

  def flush?
    return @cards if @cards.map(&:type).uniq.size == 1
  end

  def straight?
    return @cards if (vs = @cards.map(&:value).sort) == (vs.min..vs.max).to_a
  end

  def three_of_a_kind?
    x_of_a_kind?(3)
  end

  def two_pairs?
    if (first_pair = one_pair?) and (second = Hand.new(@cards - one_pair?).one_pair?)
      return first_pair + second
    else
      return false
    end
  end

  def one_pair?
    x_of_a_kind?(2)
  end

  def high_card?
    @cards.sort_by{|c| c.value}.last
  end

  private
  def x_of_a_kind?(x)
    Poker::values.each do |v|
      if (ary = @cards.select{|c| c.value == v}).size == x
        return ary
      end
    end
    return false
  end
end

Determining a poker hand with two arrays

1 Answers1