Elisp merge lists, keep order

*scratch*.el

(defun merge-lists (&rest lists)
  "Merge list, keep elements' order the same as where they are in the original lists.

E.g `(merge-list '(1 2) '(3 4 5))' should returns `(1 3 2 4 5)'."
  (let ((copy (mapcar 'copy-sequence lists))
        (result))
    (while copy
      (dolist (lst copy)
        (when-let ((elt (pop lst)))     ; pop doesn't change `lst'
          (push elt result)))
      (setq copy (remove nil copy)))
    (nreverse result)))

(defun merge-lists (&rest lists)
  "Merge list, keep elements' order the same as where they are in the original lists.

E.g `(merge-list '(1 2) '(3 4 5))' should returns `(1 3 2 4 5)'."
  (let ((copy (mapcar 'copy-sequence lists))
        (result))
    (while copy
      (dolist (lst copy)
        (pcase lst
          (`(,a ,b . ,rest) (progn
                              (push a result)
                              (setcar lst b)
                              (setcdr lst rest)))
          (`(,a) (progn
                   (push a result)
                   (setcar lst nil)
                   (setcar lst nil)))))
      (setq copy (remove '(nil) (remove nil copy))))
    (nreverse result)))