[Project Euler] Problem 17

Problem 17

綴りが間違っていると正解が出ないので、念のために数詞を調べ直したりとか、英語を使ってない我々にはそれだけで敷居が高い問題。
この手の問題を解く時は、match-case構文を便利だと特に感じる。

object P017 {

  val digitOne:List[String] = List("", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine")
  val teens:List[String] = List("", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen")
  val digitTen:List[String] = List("", "ten", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety")
  def toEnglish(n:Int):String = n match {
    case 1000 => "one thousand"
    case _ if (n/100 != 0) => digitOne(n/100)+" hundred" + (if (n%100==0) "" else " and "+toEnglish(n%100))
    case _ if (10<n)&&(n<20) => teens(n-10)
    case _ => Tuple2(n/10, n%10) match {
      case (a,0) => digitTen(a)
      case (0,b) => digitOne(b)
      case (a,b) => digitTen(a)+"-"+digitOne(b)
    }
  }
  def countLetter(s:String) = s.split("[ -]").map{s => s.length}.foldLeft(0)(_+_)
  def main(args:Array[String]) {
    /*
    println(List(1,9,10,11,19,20,21,99).map{x => Tuple3(x,toEnglish(x),countLetter(toEnglish(x)))})
    println(List(100,101,110,111,120,121,199).map{x => Tuple2(x,toEnglish(x))})
    println(List(200,201,210,211,299).map{x => Tuple2(x,toEnglish(x))})
    println(List(900,901,910,911,999,1000).map{x => Tuple2(x,toEnglish(x))})
    */
    println(List(342,115).map{x => Tuple3(x,toEnglish(x),countLetter(toEnglish(x)))})
    println(List.range(1,1001).map{x => countLetter(toEnglish(x))}.foldLeft(0)(_+_))
  }
}