Scala: How to check if all items are unique in a Seq?

问题

Is there a more idiomatic and maybe faster way to check if there are duplicates in a Seq, than this:

mySeq.size == mySeq.toSet.size

回答1:

This will be faster, because it can terminate early:

def allUnique[A](to: TraversableOnce[A]) = {
  val set = scala.collection.mutable.Set[A]()
  to.forall { x =>
    if (set(x)) false else {
      set += x
      true
    }
  }
}

来源：https://stackoverflow.com/questions/23752677/scala-how-to-check-if-all-items-are-unique-in-a-seq