Permutations: Difference between revisions
Content added Content deleted
(→{{header|Racket}}: We now have a library function, and also a faster+simpler naive impl) |
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=={{header|Racket}}== |
=={{header|Racket}}== |
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<lang |
<lang racket> |
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#lang racket |
#lang racket |
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(let loop ([l l] [tail '()]) |
(let loop ([l l] [tail '()]) |
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(if (null? l) (list tail) |
(if (null? l) (list tail) |
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(append-map ( |
(append-map (λ(x) (loop (remq x l) (cons x tail))) l)))) |
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(perms '(A B C)) |
(perms '(A B C)) |
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;; -> '((C B A) (B C A) (C A B) (A C B) (B A C) (A B C)) |
;; -> '((C B A) (B C A) (C A B) (A C B) (B A C) (A B C)) |
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