defmodule RC do
  # hash table approach
  def uniq1(list) do
    Enum.reduce(list, HashSet.new, fn x, set -> Set.put(set, x) end)
    |> Set.to_list
  end

  # Sort approach
  def uniq2(list), do: Enum.sort(list) |> uniq2([])

  defp uniq2([], uniq), do: Enum.reverse(uniq)
  defp uniq2([h|t], uniq) when h==hd(uniq), do: uniq2(t, uniq)
  defp uniq2([h|t], uniq)                 , do: uniq2(t, [h | uniq])

  # Go through the list approach
  def uniq3(list), do: uniq3(list, [])

  defp uniq3([], uniq), do: Enum.reverse(uniq)
  defp uniq3([h|t], uniq) do
    if Enum.member?(uniq, h), do: uniq3(t, uniq), else: uniq3(t, [h | uniq])
  end
end

list = [1,1,2,1,'redundant',[1,2,3],[1,2,3],'redundant']
IO.inspect Enum.uniq(list)
IO.inspect RC.uniq1(list)
IO.inspect RC.uniq2(list)
IO.inspect RC.uniq3(list)