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/*
* 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)
}
}
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