Molloy Problem

molloy.rb

#!/usr/bin/env ruby
# -*-ruby-*-

require 'pp'
require 'minitest/autorun'

class Pocket
  MAX = 16
  attr_reader :stones, :name
  
  def initialize(name, stones = [])
    @name = name
    @stones = *stones
  end

  def to_s
    "#{name}: #{@stones.to_s}"
  end

  def <<(s)
    return false unless @stones.size < MAX
    
    @stones << s
    return true
  end

  def moveStoneTo(pocket)
    return false if @stones.size == 0
    
    idx = (rand @stones.size).to_i
    e = @stones[idx]
    @stones.delete_at idx

    # actual Molloy's sucking of 'e' stone
    yield e if block_given?

    return pocket << e
  end
end

class Molloy # Java style!
  def initialize(p1, p2, p3, p4)
    @p1 = p1
    @p2 = p2
    @p3 = p3
    @p4 = p4
  end

  def self.print_pockets(*p)
    p.each {|idx| pp idx }
    puts ""
  end

  # must return an array
  def rotate
    fail "override me"
  end

  def suckStones(verbose = true)
    Molloy.print_pockets @p1, @p2, @p3, @p4 if verbose
    q = rotate
    if verbose
      Molloy.print_pockets @p1, @p2, @p3, @p4
      pp q
      pp q.size
    end
    q
  end
end

class SeasideMolloy < Molloy
  def initialize(p1, p2, p3, p4)
    super p1, p2, p3, p4
  end
  
  def rotate
    q = []
  
    while @p1.moveStoneTo(@p4) {|idx| q << idx }; end
    while @p2.moveStoneTo(@p1) {|idx| q << idx }; end
    while @p3.moveStoneTo(@p2) {|idx| q << idx }; end
    while @p4.moveStoneTo(@p3); end
    
    q
  end
end

# [1] ==> [4*]
#
#  /\      ||
#  ||      \/
#
# [2] <== [3]

class TestSeasideMolloy < MiniTest::Unit::TestCase
  def setup
    p1 = Pocket.new 1, [1, 2, 3, 4, 5, 6]
    p2 = Pocket.new 2, [7, 8, 9, 10, 11]
    p3 = Pocket.new 3, [12, 13, 14, 15, 16]
    p4 = Pocket.new 4

    @sm = SeasideMolloy.new p1, p2, p3, p4
    @sm.suckStones
  end

  def test_sucking
    256.times {
      q = @sm.suckStones false
      assert_equal Pocket::MAX, q.uniq.size
    }
  end
end