Project Euler Problem 8

problem8.scala

  /**
   * http://projecteuler.net/problem=8
   * http://odz.sakura.ne.jp/projecteuler/index.php?cmd=read&page=Problem%208
   */

  val s = "7316717 ... 63450" // 途中省略してます.
  val xs = s.toList.map(_.toString.toInt)

  def product(xs: List[Int], ys: List[Int]): List[Int] = {
    xs match {
      case a :: b :: c :: d :: e :: tail => product(xs.tail, a * b * c * d * e :: ys)
      case _ => ys
    }
  }

  val ret = product(xs, Nil) max

  println(ret)