Question

当给出一个列表时，我必须将列表拆分为将相同元素组合在一起的列表。

例如：＆＃39;（37 37 39 38 38 39 38 40 40 38）必须导致＆＃39;（（37 37）（39 39）（38 38 38 38）（40 40））

任何人都可以帮我吗？

Answer 1

这是一种方法：

(define (group lst)
  (let iter ((lst lst) (found null) (res null))
    (if (null? lst) ; all done ...
        (reverse res) ; ... return result (reversed)
        (let ((c (car lst))) ; isolate first element
          (if (member c found) ; already processed that
              (iter (cdr lst) found res) ; just go on with the next
              (iter (cdr lst) ; otherwise add this to found and create a list of as many elements ...
                    (cons c found) ; ... as found in the list to the current result ...
                    (cons (make-list (count (curry equal? c) lst) c) res))))))) ; ... and go on with the next

测试

> (group '(37 37 39 38 38 39 38 40 40 37))
'((37 37 37) (39 39) (38 38 38) (40 40))
> (group '(37 37 39 38 38 39 38 40 40 38))
'((37 37) (39 39) (38 38 38 38) (40 40))

计划列表中的组号？

1 个答案: