gistfile1.rb

ENCODE_CHARS = [*?a..?z, *?A..?Z]

def encode(n)
  6.times.map { |i|
    n, mod = n.divmod(ENCODE_CHARS.size)
    ENCODE_CHARS[mod]
  }.join
end

def encode_simplified(n)
  result = ""
  6.times do
    m = n % ENCODE_CHARS.size
    n = n / ENCODE_CHARS.size
    result << ENCODE_CHARS[m]
  end
  return result
end