Quicksort

[CALCAD]

Here is an Autolisp implementation of the Quicksort algorithm. It's been a few years, but I think I adapted this code from a C language example. I've used many different sorting routines, but Quicksort is the best for general sorts.

 

(defun qsort (inlist / pivot dpivot ppivot index list1 list2 )
     (if (<= (length inlist) 1)
        inlist
        (progn
           (setq ppivot (/ (length inlist) 2))
           (setq pivot (cdr (nth ppivot inlist)))
           (setq dpivot (nth ppivot inlist))
           (setq list1 ())
           (setq list2 ())
           (setq index 0)
           (while (< index (length inlist))
              (if (/= index ppivot)
                 (if (< (cdr (nth index inlist)) pivot)
                    (setq list1 (append list1 (list (nth index inlist))))
                    (setq list2 (append list2 (list (nth index inlist))))
                 )
              )
              (setq index (+ index 1))
           )
           (setq list1 (qsort list1))
           (setq list2 (qsort list2))
           (setq inlist (append list1 (list dpivot) list2))
        )
     )
)