jolts.scala

def part1(joltages: IndexedSeq[Int]): Int = {
    def findJolts(it: Int = 0, jo: IndexedSeq[Int] = joltages, on: IndexedSeq[Int] = IndexedSeq(), tr: IndexedSeq[Int] = IndexedSeq()): (IndexedSeq[Int], IndexedSeq[Int]) = 
        @tailrec
        def iter(i: Int, j: IndexedSeq[Int], o: IndexedSeq[Int], t: IndexedSeq[Int]): (IndexedSeq[Int], IndexedSeq[Int]) = 
            val tup = (j.sorted filter((x: Int) => (x - i == 1) | (x - i == 3))).head match {
                case x if i + 1 == x => (x, o :+ x, t)
                case x if i + 3 == x => (x, o, t:+ x)
            if (tup._2.size + tup._3.size == j.length) return (tup._2, tup._3)
            iter(tup._1, j.filter(_ != tup._1), tup._2, tup._3)
        iter(it, jo, on, tr)
    }
    val x = findJolts()
    x._1.length * x._2.length
}