#!/usr/bin/perl
#
# 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

# hanoi(peg_init, peg_dest, peg_temp, n)
sub hanoi
{
  if ($_[3] != 0)
  {
    # move n - 1 discs from peg_init to peg_temp using peg_dest as temp
    hanoi($_[0], $_[2], $_[1], ($_[3] - 1));
    
    # move nth disc from peg_init to peg_dest
    print "move disc $_[3] from peg $_[0] to peg $_[1]\n";
    
    # move n - 1 discs from peg_temp to peg_dest using peg_init as temp
    hanoi($_[2], $_[1], $_[0], ($_[3] - 1));
  }
}

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

if (($#ARGV != 0) && ($#ARGV != 3))
{
  print "usage: hanoi.pl <number of discs> [<initial peg> <destination peg> <temp peg>]\n";
  exit 1;
}

# is n a number?
if ($ARGV[0] !~ /^[0-9]+$/)
{
  print "first argument must be a positive integer\n";
  exit 2;
}

if ($#ARGV == 3)
{
  $peg_init = $ARGV[1];
  $peg_dest = $ARGV[2];
  $peg_temp = $ARGV[3];
}

hanoi($peg_init, $peg_dest, $peg_temp, $ARGV[0]);

exit 0;