swap-count.lisp

(defmacro for (data &rest body)
  (let* ((var   (first data))
         (start (second data))
         (stop  (third data))
         (gstop (gensym)) )
    `(do ((,var ,start (1+ ,var))
          (,gstop ,stop))
         ((> ,var ,gstop))
       ,@body)))
       
(defun calc5 (lst)
  (let* ((len (length lst))
         (ary (apply #'vector lst))
         (table (make-array (list len) :element-type 'bit :initial-element 0))
         (swap-way '())
         (count 0))
    (for (i 0 (1- len))
      (when (zerop (aref table i))
        (do ((j (aref ary i) (aref ary j)))
            ((= i j))
          (push (list i j) swap-way)
          (incf count)
          (setf (aref table j) 1))
        (setf (aref table i) 1)))
    (list count (reverse swap-way))))

;; (calc5 '(1 2 3 0 5 6 7 4))
;=> (6 ((0 1) (0 2) (0 3) (4 5) (4 6) (4 7)))