降雨趣题 Scala 实现 http://www.ituring.com.cn/article/273313

Count.scala

object Count extends App {
  def sliceFromMaxElement(array: Array[Int]) = {
    val (left, right) = array.span(_ < array.max)
    (left, right.tail.reverse)
  }

  def fold(array: Array[Int], result: Int = 0): Int = {
    if (array.isEmpty) {
      result
    } else {
      val (left, right) = sliceFromMaxElement(array)
      fold(left, right.fold(result)((sum, i) => sum + array.max - i))
    }
  }

  def calculate(seq: Array[Int] = Array(0)): Int = {
    val (left, right) = sliceFromMaxElement(seq)
    fold(left) + fold(right)
  }

  override def main(args: Array[String]): Unit = {
    if(args.isEmpty){
      println(calculate(Array(0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1)))
    } else {
      println(calculate(args.map(_.toInt)))
    }
  }
}