Turnstile.scala

object Turnstile {

  def getTimes(time: Array[Int], direction: Array[Int]): Array[Int] = {
    var lt = -1
    var ld = 1
    val result = Array.fill(time.length) { 0 }

    time.foldLeft(time.zipWithIndex) { (q, _) =>
      val nt = q.head._1

      val (taken, dir) = if (nt - lt > 1) {
        // no previous second usage
        (
          q.takeWhile(v => v._1 == nt),
          1
        )
      } else {
        (
          q.takeWhile(v => v._1 - lt <= 1),
          ld
        )
      }

      val next = taken.find(v => direction(v._2) == dir).getOrElse(taken.head)

      lt = if (next._1 > lt + 1) next._1 else lt + 1
      ld = direction(next._2)
      result(next._2) = lt

      taken.filter(_ != next) ++ q.drop(taken.length)
    }

    result
  }

  def main(args: Array[String]): Unit = {
    val result = getTimes(Array(1, 1, 1, 4, 4, 4, 7, 7, 7), Array(0, 1, 0, 1, 1, 0, 1, 1, 0))
    println(result.toList)
    println(result equals Array(1))
  }
}