HW2.ex

defmodule HW1 do
  def flatten([]), do: []
  def flatten([head | []]), do: [head]
  def flatten([[head] | [tail]]), do: [head | flatten(tail)]
  def flatten([head | [tail]]), do: [head | flatten(tail)]
  def flatten([head | tail]), do: [head | flatten(tail)]
  def flatten(head), do: [head]
end