ruby permutations

shuffle.rb

def shuffle(number)
  ret_arr = []
  f = fact(number.to_s.size)
  count = 0
  while count < f/2 do
    if count == 0
      ret_arr.push(number)
      ret_arr.push(number.to_s.reverse.to_i)
    else
      num_arr = number.to_s.split(//)
      last = num_arr.shift
      num_arr.push(last)
      number = num_arr.join.to_i
      reverse_number = num_arr.reverse.join.to_i

      ret_arr.push(number)
      ret_arr.push(reverse_number)
    end
    count += 1
  end
  p ret_arr.sort!
end

def fact(number)
  ret = 1
  while number > 0
    ret *= number
    number -= 1
  end
  return ret
end

shuffle(1234)