permutation.scala

object main extends App {
  def perm[T](xs: List[T]): Seq[List[T]] = {
    val len = xs.size
    if (len < 2) List(xs)
    else
      (0 until len).flatMap { i =>
        val (head, tail) = (xs(i), xs.take(i) ++ xs.drop(i + 1))
        perm(tail).foldLeft(List[List[T]]())((r, p) => (head :: p) :: r)
      }
  }
  println(s"Permutation: ${perm(List('a', 'b', 'c'))}")
}