samgj18

def sorted[S >: T](implicit ordering: Ordering[S]): List[S] = {

    /**
      * sort(4, [], [1, 2, 3, 5])
      * sort(4, [1], [2, 3, 5])
      * sort(4, [2, 1], [3, 5])
      * sort(4, [3, 2, 1], [5])
      * [3, 2, 1].reverse ++ (4 :: [5])
      */
    @tailrec