simple quick sort

qsort.scala

scala> def qsort(xs: List[Int]): List[Int] = {
     |   if (xs.length <= 1) xs
     |   else {
     |     val pivot = xs(xs.length / 2)
     |     qsort(xs filter (_ < pivot)) ++ List(pivot) ++ qsort(xs filter (_ > pivot))
     |   }
     | }
qsort: (xs: List[Int])List[Int]