方案排序列表不同的标准 [英] scheme sort list diffent criteria
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问题描述
我有一个有限的四元组列表,例如
I have a finite list of quadruples, e.g.
(list (list 1 3 5 5) (list 2 3 4 9) (list 3 4 4 6)(list 4 7 10 3)).
我用 (a1 a2 a3 a4) 表示每个元素.
I denote each of the elements by (a1 a2 a3 a4).
请帮我写一个排序函数,它提供根据以下标准创建的递增"列表:
Please help me to write a sorting function which provides a "increasing" list created according to the following criteria:
- 数字a2,
- 后来的差异(a3 - a4),
- 然后是数字 a3.
如果可以,请帮忙.
推荐答案
据我所知,您的排序条件就是排序的顺序.如果是这种情况,则以下程序应执行该排序.
As far as I can tell, your ordered criteria are the order in which to sort. If this is the case, then the following program should perform that sorting.
(define (strange-sort quadruples)
(define (a2 quad)
(cadr quad))
(define (a3 quad)
(caddr quad))
(define (a4 quad)
(cadddr quad))
(sort quadruples
(lambda (x y)
(cond ((< (a2 x) (a2 y))
#t)
((> (a2 x) (a2 y))
#f)
(else
(cond ((< (- (a3 x) (a4 x))
(- (a3 y) (a4 y)))
#t)
((> (- (a3 x) (a4 x))
(- (a3 y) (a4 y)))
#f)
(else
(cond ((< (a3 x) (a3 y))
#t)
(else #f)))))))))
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