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Ingy döt Net 2013-04-11 01:07:29 -07:00
parent b83f433714
commit 68f8f3e56b
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21
Task/Sorting-algorithms-Gnome-sort/Scheme/sorting-algorithms-gnome-sort.ss Normal file
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; supply comparison function, which returns true if first and second
; arguments are in order or equal.
(define (gnome-sort-compar in-order input-list)
(let gnome ((p (list (car input-list)))
(n (cdr input-list)))
(if (null? n) ; no more flowerpots?
p ; we're done
(let ((prev-pot (car p))
(next-pot (car n)))
(if (in-order next-pot prev-pot)
; if the pots are in order, step forwards.
; otherwise, exchange the two pots, and step backwards.
(gnome (cons next-pot p) ; Prev list grows
(cdr n)) ; Next list shorter by one
(if (null? (cdr p)) ; are we at the beginning?
(gnome ; if so, we can't step back
(list next-pot) ; simply exchange the pots without
(cons prev-pot (cdr n))) ; changing lengths of lists
(gnome
(cdr p) ; Prev list shorter by one
(cons next-pot (cons prev-pot (cdr n))))))))))