Towers of Hanoi solution in ruby

towers of hanoi code

require 'minitest/spec'
require 'minitest/autorun'

describe 'Game' do
 it 'should have 3 pegs' do
   game = Game.new
   game.pegs.count.must_equal 3
 end
 
 it 'should have 3 discs by default' do
   game = Game.new
   game.discs.count.must_equal 3
 end
 
 it 'should be able to have 4 discs' do
   game = Game.new(4)
   game.discs.count.must_equal 4
 end
 
 it 'should start with all discs on source peg' do
   game = Game.new
   game.source.discs.count == 3
   game.dest.discs.count == 0
   game.spare.discs.count == 0
 end
 
 it 'should have correct number of moves and be finished' do
   (3..10).each do |n|
    game = Game.new(n)
    game.play
    game.number_moves.must_equal (2**n - 1)
    game.dest.discs.length.must_equal n
    v = 1
    game.dest.discs.each do |d|
      d.must_equal v
      v += 1
    end
   end
 end
 
 it 'should have 0 moves before playing' do
    game = Game.new
    game.number_moves.must_equal 0
 end
  
 it 'should have correct # moves for 3 discs' do
   game = Game.new
   game.play
   game.number_moves.must_equal (2**game.number_discs - 1)
 end
   
 it 'should have correct # moves for 4 discs' do
   game = Game.new(4)
   game.play
   game.number_moves.must_equal (2**game.number_discs - 1)
 end
end

class Peg
  attr_accessor :last_location
  
  def initialize
    @discs = []
    @last_location = nil
  end
  
  def add_discs(arr)
    @discs = arr
  end
  
  def discs
    @discs
  end
end

SOURCE_INDEX = 0
SPARE_INDEX = 1
DEST_INDEX = 2


class Game
  attr_accessor :pegs, :discs, :number_moves, :number_discs
  def initialize(disc_count = 3)
    @discs = []
    (1..disc_count).each do |n|
      @discs << n
    end
    @pegs = [Peg.new, Peg.new, Peg.new]
    @pegs[0].add_discs(@discs)
    @number_moves = 0
    @number_discs = @discs.length
  end
  
  def show
    puts "\ngame output:"
    @pegs.each_with_index do |p, idx|
      puts "Peg: #{idx}      ----  discs: #{p.discs}"
    end
  end
  
  def play
    self.show   
    @number_moves = 0     
    process_game(@pegs[SOURCE_INDEX], @pegs[DEST_INDEX], @pegs[SPARE_INDEX], @number_discs)
    puts "\n\n DONE:"
    puts "number moves: #{@number_moves}"
  end 
  
  
  def process_game(src_peg, dest_peg, spare_peg, number_left)
    if number_left == 1
      disc = src_peg.discs.pop
      dest_peg.discs.push disc
      @number_moves += 1
      self.show
    else
      process_game(src_peg, spare_peg, dest_peg, number_left - 1)
      process_game(src_peg, dest_peg, spare_peg, 1)
      process_game(spare_peg, dest_peg, src_peg, number_left - 1)
    end
  end
  
  def source
    @pegs[0]
  end
  
  def dest
    @pegs[2]
  end
  
  def spare
    @pegs[1]
  end
end