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use sort to implement quicksort

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svn: r4682
This commit is contained in:
Eli Barzilay 2006-10-25 17:10:05 +00:00
parent 60fe398868
commit 23882b3fac
1 changed files with 6 additions and 32 deletions
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38
collects/mzlib/list.ss
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@ -36,8 +36,8 @@
filter filter
quicksort quicksort ; deprecated
mergesort mergesort ; deprecated
sort sort
sort! sort!
merge-sorted-lists merge-sorted-lists
@ -128,7 +128,7 @@
[else '()])) [else '()]))
(unless (list? lst) (unless (list? lst)
(raise-type-error who "proper list" lst)) (raise-type-error who "proper list" lst))
(unless (procedure-arity-includes? less? 2) (unless (and (procedure? less?) (procedure-arity-includes? less? 2))
(raise-type-error who "procedure of arity 2" less?)) (raise-type-error who "procedure of arity 2" less?))
(let ([n (length lst)]) (let ([n (length lst)])
(cond [(<= n 1) lst] (cond [(<= n 1) lst]
@ -142,37 +142,11 @@
[else (when copy? (set! lst (append lst '()))) [else (when copy? (set! lst (append lst '())))
(step n)]))) (step n)])))
(define (sort! lst less?) (define (sort! lst less?) (sort-internal lst less? #f 'sort!))
(sort-internal lst less? #f 'sort!)) (define (sort lst less?) (sort-internal lst less? #t 'sort))
(define (sort lst less?)
(sort-internal lst less? #t 'sort))
;; deprecated!
(define (quicksort l less-than)
(unless (list? l)
(raise-type-error 'quicksort "proper list" l))
(unless (procedure-arity-includes? less-than 2)
(raise-type-error 'quicksort "procedure of arity 2" less-than))
(let* ([v (list->vector l)]
[count (vector-length v)])
(let loop ([min 0][max count])
(if (< min (sub1 max))
(let ([pval (vector-ref v min)])
(let pivot-loop ([pivot min] [pos (add1 min)])
(if (< pos max)
(let ([cval (vector-ref v pos)])
(if (less-than cval pval)
(begin (vector-set! v pos (vector-ref v pivot))
(vector-set! v pivot cval)
(pivot-loop (add1 pivot) (add1 pos)))
(pivot-loop pivot (add1 pos))))
(if (= min pivot)
(loop (add1 pivot) max)
(begin (loop min pivot)
(loop pivot max))))))))
(vector->list v)))
;; deprecated! ;; deprecated!
(define quicksort sort)
(define mergesort sort) (define mergesort sort)
(define remove (define remove