答复: 有1元，5元，10元，20元，50元，问组成100元有多少种情况
SICP, 1.2.2Tree Recursion有详细的解释
http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-11.html#%_sec_1.2.2
CLISP的一种实现
(defparameter us-coins (list 50 25 10 5 1))(defun no-more? (coin-values)(null coin-values))(defun except-first-denomination (coin-values)(cdr coin-values))(defun first-denomination (coin-values)(car coin-values))(defun cc (amount coin-values)(cond ((= amount 0) 1) ((or (< amount 0) (no-more? coin-values)) 0) (t (+ (cc amount (except-first-denomination coin-values)) (cc (- amount (first-denomination coin-values)) coin-values)))))(defun count-change (amount &optional (coin-values us-coins))(cc amount coin-values));;; test, assertEquals 343(print (count-change 100 '(50 20 10 5 1)))
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