Scala String Equality Question from Programming Interview

Question

Since I liked programming in Scala, for my Google interview, I asked them to give me a Scala / functional programming style question. The Scala functional style question that I

Answer 1

If the goal is minimal memory footprint, it's hard to argue against iterators.

def areSame(a :String, b :String) :Boolean = {
  def getNext(ci :Iterator[Char], ignore :Int = 0) : Option[Char] =
    if (ci.hasNext) {
      val c = ci.next()
      if (c == '/')        getNext(ci, ignore+1)
      else if (ignore > 0) getNext(ci, ignore-1)
      else                 Some(c)
    } else None

  val ari = a.reverseIterator
  val bri = b.reverseIterator
  1 to a.length.max(b.length) forall(_ => getNext(ari) == getNext(bri))
}

On the other hand, when arguing FP principals it's hard to defend iterators, since they're all about maintaining state.