let rec qSort (s:int list) =
    if s.Length = 0 then
        []
    elif s.Length = 1 then
        s
    else
        let x = s.[System.Random().Next(s.Length - 1)]
        List.append (qSort(List.filter(fun y -> y < x) s)) (List.append (List.filter (fun y -> y = x) s) (qSort(List.filter(fun y -> y > x) s)))