finding sum of two largest values in list (unordered).

two_largest

val sample = List(1,2,3,3,5,4,6,7,4)
 
// a good default if sample is always positive integers.
val START = (-1, -1) 

// this is what I meant by default foldLeft (or scanLeft) value
val two_largest = test.foldLeft(START) { (acc: (Int, Int), n: Int) =>
  val (smaller, larger) = acc
  if (n > larger) 
    (larger, n)
  else if (n > smaller)
    (n, larger)
  else
    (smaller, larger)
}
 
// ANSWER:
 
two_largest._1 + two_largest._2

note that this doesn't incorporate case when list is length 1 properly. could probably start with 0s