硬貨の問題.lisp

(defparameter *coins* `(1 5 10 50 100 500))
(defparameter *have-coins* `(3 2 1 3 0 2))
(defparameter *sum* 620)

(defun calc (index sum answer)
    (let* ((number (min (floor sum (nth index *coins*)) (nth index *have-coins*)))
              (new-sum (- sum (* number (nth index *coins*))))
              (new-answer (+ answer number)))
        (values new-sum new-answer)))

(defun coins (index sum answer)
    (if (equalp index -1)
        answer
        (multiple-value-bind (new-sum new-answer) (calc index sum answer)
            (coins (1- index) new-sum new-answer))))

(defun solve ()
    (let ((total (coins 5 *sum* 0)))
        (format nil "~D" total)))