package kapitel_03

/**
 * Beispiel aus
 *
 * - Algorithmen und Datenstrukturen für Dummies
 *   - von Andreas Gogol-Döring und Thomas Letschert
 *   - Verlag Wiley-VCH; Oktober 2019
 *  - Kapitel 3, Daten und ihre Struktur
 *
 * @author A. Gogol-Döring, Th. Letschert
 */

import scala.annotation.tailrec

object AuD_03_07_FIter_App extends App {

  def FItera(n: Int): Int = {
    var acc1: List[Int] = Nil
    var nV = n
    while (nV != 0) {
      acc1 = nV :: acc1
      nV = nV - 1
    }
    var acc2 = 1
    var rev = acc1
    while (rev != Nil)
      rev match {
        case head :: rest =>
          acc2 = acc2 * head
          rev = rest
        case _ =>
      }
    acc2
  }


  def FTR(n: Int): Int = {
    @tailrec
    def f(n: Int, acc: Int): Int =
      if (n == 0) acc
      else f(n-1, acc * n)

    f(n, 1)
  }

  def FIter(n: Int): Int = {
    var f = 1
    var nV = n
    while (nV != 0) {
      val (n_, f_) = (nV-1, nV * f)
      nV = n_
      f = f_
    }
    f
  }

  println(FTR(10))
  println(FIter(10))
  println(FItera(10))

}