Functional Programming: Does a list only contain unique items?

Question

I\'m having an unsorted list and want to know, whether all items in it are unique.
My naive approach would be

val l = List(1,2,3,4,3)
def isUniqueList(l: List[Int         


        

Answer 1

I would simply use distinct method:

scala> val l = List(1,2,3,4,3)
l: List[Int] = List(1, 2, 3, 4, 3)

scala> l.distinct.size == l.size
res2: Boolean = false

ADD: Standard distinct implementation (from scala.collection.SeqLike) uses mutable HashSet, to find duplicate elements:

  def distinct: Repr = {
    val b = newBuilder
    val seen = mutable.HashSet[A]()
    for (x <- this) {
      if (!seen(x)) {
        b += x
        seen += x
      }
    }
    b.result
  }