package hacker

object doodle {

  def f(arr:List[Int]): List[Int] = {
    if (arr.length == 1) List.concat( arr )
    else{
    List.concat( arr.takeRight(1), f(arr.dropRight(1)) )
     }
   }                                              //> f: (arr: List[Int])List[Int]

   f(List(10,11,2,1))                             //> res0: List[Int] = List(1, 2, 11, 10)

}