金币找零问题：（递归方法）

(defun coin  (key)
(cond ((= 1 key) 1)
      ((= 2 key) 5)
      ((= 3 key) 10)
      ((= 4 key)  20)
      ((= 5 key) 50)
      (t 0)
))

 

(defvar stack1 nil)
(setq stack1 nil)

(defun action (account )
(let ((value (pop stack1)))
  (if ( or (> (- account  (if value
    value
         0)) 0 )
    (= (- account  (if value
    value
         0)) 0 ))
      (prog1
 (if (> (if value
      value
   (setq value 0))
        0)
     (prog1 (print value)
       (if (= account 0) (push value stack1))
       (if (> account 0)
       (action (- account value )))
     )
 ))
    (push value stack1)
    )))

(defun cc (account kinds-of-coin)
  (push  (coin kinds-of-coin) stack1)
  (cond ((= 0 account) (prog1 1
    (pop stack1)
;;    (action 20)
    ))
 ((or (< account  0) (= kinds-of-coin 0)) (prog1 0
         (pop stack1)
         ))
 (t (+ (cc account
    (- kinds-of-coin 1))
       (cc (- account (coin kinds-of-coin))
    kinds-of-coin
    )))))

(prog1 (setq stack1 nil)
(setq counter (cc 20 5)))