stringperm.rb

=begin
STRING PERMUTATIONS
CHALLENGE DESCRIPTION:
Write a program which prints all the permutations of a string in alphabetical order. We consider that digits < upper case letters < lower case letters. The sorting should be performed in ascending order.
INPUT SAMPLE:
Your program should accept a file as its first argument. The file contains input strings, one per line.
For example:
hat
abc
Zu6
OUTPUT SAMPLE:
Print to stdout the permutations of the string separated by comma, in alphabetical order.
For example:
aht,ath,hat,hta,tah,tha
abc,acb,bac,bca,cab,cba
6Zu,6uZ,Z6u,Zu6,u6Z,uZ6
=end

lines = File.readlines(ARGV[0])

lines.each do |line|
  strings = []
  line.chomp.chars.permutation.each do |perm|
    strings << perm.join
  end
  puts strings.sort.join(",")
end