Question

(defun rep(list)
(format t"~a~%" list)
    (cond
        ((null list) nil)
        ((atom (car list)) (cons (car list) (rep  (cdr list))))
        ((listp (car list))  (cons (car (reverse (car list))) (cdr list)))
        (t (rep list))
    )
)

编写一个函数，用最后一个元素替换列表的每个子列表。子列表是第一级的元素，它是一个列表。示例：

(a (b c) (d (e (f)))) ==> (a c (e (f))) ==> (a c (f)) ==> (a c f)
     (a (b c) (d ((e) f))) ==> (a c ((e) f)) ==> (a c f)

我有以上问题要解决。得到它直到一点但我被卡住了。显然它没有进入列表中的下一个元素，我不知道为什么。有什么想法吗？

Answer 1

我会这样打破它：

(defun last-element (lst)
  (if (listp lst)
    (last-element (car (last lst)))
    lst))

(defun rep (lst)
  (when lst
    (cons (last-element (car lst)) (rep (cdr lst)))))

然后

(rep '(a (b c) (d (e (f)))))
=> '(A C F)

Answer 2

没有使用地图功能

(defun rep(list)
    (cond
        ((null list) nil)
        ((listp (car list)) (rep (cons (car (reverse (car list))) (rep (cdr list)))))
        (t (cons (car list) (rep (cdr list))))
    )
)

用最后一个元素替换子列表

2 个答案: