ReadPhoneNumber.scala

object ReadPhoneNumber extends App {

  def read(number: String, format: List[Int]): String = convert {
    formatting(number, format) flatMap runLength
  }

  def convert(runLength: List[(Int, Int)]): String = {

    val NUMBER_TO_STRING = "zero one two three four five six seven eight nine" split ' '
    val COUNT_STRING = "double triple quadruple quintuple sextuple septuple octuple nonuple decuple" split ' '
    runLength.map {
      case (n, r) if r > 10 => List.fill(r)(NUMBER_TO_STRING(n)) mkString " "
      case (n, r) if r > 1 => COUNT_STRING(r - 2) + " " + NUMBER_TO_STRING(n)
      case (n, r) => NUMBER_TO_STRING(n)
    } mkString " "
  }

  def formatting(number: String, format: List[Int]): List[List[Int]] = ((List.empty[String], number) /: format) {
    case ((acc, number), count) => ((number take count) :: acc, number drop count)
  }._1.reverse.map(_.map(_ - '0').toList)

  def runLength(number: List[Int]): List[(Int, Int)] = (List.empty[(Int, Int)] /: number) {
    case ((n, r) :: xs, digit) if n == digit => (n, r + 1) :: xs
    case (acc, digit) => (digit, 1) :: acc
  }.reverse

  def process(iter: Iterator[String])(lineOut: String => Unit) = for (i <- 1 to iter.next().toInt) {
    val Array(n, f) = iter.next() split ' '
    lineOut(s"Case #$i: ${read(n, (f split '-').map(_.toInt).toList)}")
  }

  val writer = new java.io.PrintWriter("a.out")
  try {
    process(io.Source.fromFile("A-large-practice.in").getLines)(writer.println)
  } finally {
    writer.flush(); writer.close()
  }

}