$n = 11

​

$towers = {}

​

$idx = {a: 1, b: 2, c: 3}

​

def init

  $towers = {

    a: 1.upto($n).to_a.reverse,

    b: [],

    c: []

  }

end

​

init()

​

def stat()

  ts = [:a, :b, :c]

  puts ts.join("\t")

  ($n - 1).downto(0).each do |i|

    [:a, :b, :c].each do |t|

      print "#{$towers[t][i]}\t"

    end

    puts

  end

end

​

def m(from, to)

  d = $towers[from].pop

  dest_d = $towers[to].last

  if (to == :b && d == 1) || (dest_d && d > dest_d)

    puts("illegal move")

    exit(0)

  end

  $towers[to].push(d)

  puts "#{d} #{$idx[from]} #{$idx[to]}"

end

​

​

def move_right

  m(:a,:c)

  m(:a,:b)

  m(:c,:a)

  m(:b,:c)

  m(:a,:c)

end

​

def move_left

  m(:c,:a)

  m(:c,:b)

  m(:a,:c)

  m(:b,:a)

  m(:c,:a)

end

​

def swap()

  da = $towers[:a].last.to_i

  db = $towers[:b].last.to_i

  dc = $towers[:c].last.to_i

​

  ts = [da, db, dc]

​

  idx = [:a, :b, :c]

​

  ts.each_with_index do |d, i|

    next if d == 0 || d == 1

​

    ts.each_with_index do |dd, ii|

      next if dd == d

​

      if dd == 0 || d < dd

        return [idx[i], idx[ii]]

      end

    end

  end

end

​

​

def done?()

  $towers[:a].last == nil && $towers[:b].last == nil

end

​

def solve

  while true

    move_right

    break if done?()

    m(*swap())

    move_left

    m(*swap())

  end

end

​

stat()

solve()

stat()