#!/usr/bin/env ruby
# -*- ruby -*-
#
# Public Domain -- Christian Neukirchen 2001
#
# Prove the theorem:
#     Add a number to it's reverse unless the sum is ``symetric''.
#     That should be possible for all numbers.
#
# Examples:
# 1)
#     34 + 43 = 77;
# So 34 is ok.
#
# 2)
#     546 + 645 = 1191
#     1191 + 1911 = 3102
#     3102 + 2013 = 5115;
# So 546 is ok.
#
#
# Try 196 ;-)    [Hint: It needs more than 10000 steps (!)]
#

# Is 's' symetric?
# Examples:
#   symetric?('6565') => false
#   symetric?('7465') => false
#   symetric?('5665') => true
#   symetric?('898')  => true
def symetric? (str)
  0.upto ((str.length-1) / 2) {
    |i|				# `i' is the iterator
    return false if str[i] != str[-i-1]
  }
  true				# else return true
end

if ARGV[0].to_i != 0
  num = ARGV[0].to_i		# Take the number from the command line.
else
  num = (rand * 100000).round	# If none given, use a random one.
end

print "The number ", num, ":\n"

cnt = 0
res = num

while (!symetric? res.to_s)
  cnt += 1			# Increase the # of steps.
  printf "[%4d]\n ", cnt
  rev = num.to_s.reverse
#  print num, " + ", rev, " = "
  res = num + rev.to_i
  num = res
#  printf "%d\t(Step %4d)\n", res, cnt
end

print res
print "is ok (", cnt, " steps, len = ", num.to_s.length, ")\n"