toRubyでやったパズル

pz.rb

class Puzzle
  def initialize(n=3)
    @size = n
    @goal = (n ** 2).times.to_a.rotate
  end

  def resolve(start)
    raise 'invalid size' unless start.size == @goal.size
    visited = Set.new
    queue = [[start]]
    while path = queue.shift
      return path if path.last == @goal
      movable(path.last) do |board|
        next if visited.include?(board)
        visited << board
        queue << path + [board]
      end
    end
    nil
  end

  def movable(board)
    cur = board.index(0)
    div, mod = cur.divmod(@size)
    yield(move(board, cur, -1)) unless mod == 0
    yield(move(board, cur, 1)) unless mod == @size - 1
    yield(move(board, cur, -@size)) unless div == 0
    yield(move(board, cur, @size)) unless div == @size - 1
  end

  def move(board, index, delta)
    ary = board.dup
    ary[index], ary[index + delta] = ary[index + delta], ary[index]
    ary
  end
end

pz = Puzzle.new
path = pz.resolve(9.times.to_a.sort_by {rand})

require 'pp'
PP.pp(path&.map {|x| x.each_slice(3).to_a}, $>, 14)

require 'set'が必要なバージョンもありそう