rot13.rb

class ROT13
  def self.translate(string)
    output = string.split('').map do |character|
      if alphabet.include? character
        alphabet[(alphabet.index(character) + 13) % 26]
      else
        character
      end
    end.join
    
    puts output
  end
  
  def self.alphabet
    ('a'..'z').to_a
  end
end