Scala example source code file (fannkuch.scala)

This example Scala source code file (fannkuch.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

array, array, int, int, list, list, pfannkuchen, pfannkuchen

The Scala fannkuch.scala source code

/*
 * The Computer Language Shootout
 * http://shootout.alioth.debian.org/
 *
 * contributed by Andrei Formiga
 */

object fannkuch
{
  var permN: Int = 0
  var maxFlips: Int = 0

  def flips(l: List[Int]): Int = (l: @unchecked) match { // bq: suppress warning
    case 1 :: ls => 0
    case n :: ls => flips((l take n reverse) ::: (l drop n)) + 1
  }

  def rotateLeft(l: List[Int]) = 
    l match { case List() => List() case x :: xs => xs ::: List(x) }

  def printPerm(perm: List[Int]) = 
    { perm foreach(x => Console.print(x.toString())); Console.println; }

  def processPerm(perm: List[Int]) = {
    val f = flips(perm)
    if (f > maxFlips) maxFlips = f
    if (permN < 30) { printPerm(perm); permN = permN + 1; }
  }

  def permutations(l: List[Int], n: Int, i: Int) {
    if (i < n) {
      if (n == 1)
	processPerm(l)
      else { 
	permutations(l, n - 1, 0)
	permutations(rotateLeft(l take n) ::: (l drop n), n, i + 1)
      }
    }
  }

  def main(args: Array[String])
  {
    val n = Integer.parseInt(args(0))

    permutations(List.range(1, n + 1), n, 0)
    Console.println("Pfannkuchen(" + n + ") = " + maxFlips)
  }
}