#!/usr/bin/python
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# Copyright (C) 2008 Vino Fernando Crescini  <vfcrescini@gmail.com>

# Towers of Hanoi

import sys;
import re;

# hanoi(peg_init, peg_dest, peg_temp, n)
def hanoi(a, b, c, n):
  if n > 0:
    # move n - 1 discs from peg_init to peg_temp using peg_dest as temp
    hanoi(a, c, b, n - 1)

    # move nth disc from peg_init to peg_dest
    print "move disc", n, "from peg", a, "to peg", b

    # move n - 1 discs from peg_temp to peg_dest using peg_init as temp
    hanoi(c, b, a, n - 1)

peg_init = "init"
peg_dest = "dest"
peg_temp = "temp"

if len(sys.argv) != 2 and len(sys.argv) != 5:
  print "usage: hanoi.pl <number of discs> [<initial peg> <destination peg> <temp peg>]"
  sys.exit(1)

# is n a number?
if re.compile("^[0-9]+$").match(sys.argv[1]) is None:
  print "first argument must be a positive integer"
  sys.exit(2)

if len(sys.argv) == 5:
  peg_init = sys.argv[2]
  peg_dest = sys.argv[3]
  peg_temp = sys.argv[4]

hanoi(peg_init, peg_dest, peg_temp, int(sys.argv[1]))

sys.exit(0);