find first singleton in list

challenge.ex

  def first_singleton(list) do
    list
    |> Enum.sort()
    |> no_partner?()
  end

  def no_partner?([value | remaining_values]) do
    if value == hd(remaining_values) do
      Enum.reject(remaining_values, &(&1 == value))
      |> no_partner?()
    else
      value
    end
  end