如何对方案中的数字无序列表进行排序 [英] How to sort disorder list of numbers in scheme

问题描述

用Scheme 中的值对列表进行排序的正确方法是什么?例如，我有未排序的值:

What it the proper way to sort a list with values in Scheme? For example I have the values which are not ordered:

x1, x5, x32 .... xn

或

3, 4, 1, 3, 4, .. 9

首先我想为它们增加数字并按以下顺序显示它们:

First I want to for them by increase number and display them in this order:

x1, xn, x2, xn-1

或

1, 6, 2, 5, 3, 4

任何帮助都是有价值的.

Any help will be valuable.

推荐答案

这与您发布的问题相同 之前，但稍有改动.正如我在答案的评论中告诉您的那样，您只需在重新排列列表之前对其进行排序.这是一个球拍解决方案:

This is the same question you posted before, but with a small twist. As I told you in the comments of my answer, you just have to sort the list before rearranging it. Here's a Racket solution:

(define (interleave l1 l2)
  (cond ((empty? l1) l2)
        ((empty? l2) l1)
        (else (cons (first l1)
                    (interleave l2 (rest l1))))))

(define (zippy lst)
  (let-values (((head tail) (split-at
                             (sort lst <) ; this is the new part
                             (quotient (length lst) 2))))
    (interleave head (reverse tail))))

它按预期工作:

(zippy '(4 2 6 3 5 1))
=> '(1 6 2 5 3 4)

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