Generate letters to represent number using ruby?

Question

I would like to generate a sequence of letters i.e. \"A\", \"DE\" \"GJE\", etc. that correspond to a number. The first 26 are pretty easy so 3 returns \"C\", 26 returns \"Z\

Answer 1

class Numeric
  Alph = ("a".."z").to_a
  def alph
    s, q = "", self
    (q, r = (q - 1).divmod(26)); s.prepend(Alph[r]) until q.zero?
    s
  end
end

3.alph
# => "c"
26.alph
# => "z"
27.alph
# => "aa"
4123.alph
# => "fbo"