(defun collect-with-indexes (seq predicate)
  (loop for i from 0 upto (1- (length seq))
        for e = (elt seq i)
        when (funcall predicate e)
          collect e into elements
          and collect i into indexes
        finally (return (values elements indexes))))
 
(defun odai-pt11-77 (seq selector comparer &key key)
  (multiple-value-bind (targets indexes)
      (collect-with-indexes seq selector)
    (loop for e in (sort targets comparer :key key)
          for i in indexes
          do (setf (elt seq i) e))
    seq))
 
(let ((s "213cba213cba213cba"))
  (format t "~@{~S~%~}"
          (odai-pt11-77 (copy-seq s) #'alpha-char-p #'char<)
          (odai-pt11-77 (copy-seq s) #'digit-char-p #'char<)))
 

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