DeliveryHero_task5.scala

  def maxRun(a: Array[Int]): Int = if (a.length < 2) a.length else {
    val (totalMaxRun, (prevRun, _)) = a.tail.foldLeft(1 -> (1, a.head)) {
      case ((maxRun, (currRun, prevNum)), currNum) if Math.abs(currNum - prevNum) == 1 =>
        Math.max(maxRun, currRun + 1) -> (currRun + 1, currNum)

      // currNum doesn't belongs to currRun
      case ((maxRun, (currRun, prevNum)), currNum) => Math.max(maxRun, currRun) -> (1, currNum)
    }
    Math.max(totalMaxRun, prevRun)
  }