gistfile1.rb

class ConvertsNumberAlphaID
  ALPHAS = %w( a b c d e f 
               g h i j k l 
               m n o p q r 
               s t u v w x 
               y z 0 1 2 3 
               4 5 6 7 8 9 
               A B C D E F 
               G H I J K L 
               M N O P Q R 
               S T U V W X 
               Y Z )
  BASE = ALPHAS.length
  
  def self.from_number(number)
    out = ""
    
    shifted_number = Math.log(number, BASE).floor
    while shifted_number >= 0
      powered_base = (BASE ** shifted_number)
      index = (number / powered_base).floor % BASE
      out = ALPHAS[index] + out
      number = number - (index * powered_base)
      
      shifted_number -= 1
    end
    
    out
  end
end