30 lines
1.1 KiB
Racket
30 lines
1.1 KiB
Racket
#lang racket
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(define (s-of-n-creator n)
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(let* ([count 0] ; 'i' in the description
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[vec (make-vector n)]) ; store the elts we've seen so far
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(lambda (item)
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(if (< count n)
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; we're not full, so, kind of boring
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(begin
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(vector-set! vec count item)
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(set! count (+ count 1))
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(vector-copy vec 0 count))
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; we've already seen n elts; fun starts
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(begin
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(set! count (+ count 1))
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(when (< (random) (/ n count))
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(vector-set! vec (random n) item))
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(vector-copy vec))))))
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(define counts (make-hash '((0 . 0) (1 . 0) (2 . 0) (3 . 0) (4 . 0) (5 . 0) (6 . 0) (7 . 0) (8 . 0) (9 . 0))))
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(for ([iter (in-range 0 100000)]) ; trials
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(let ([s-of-n (s-of-n-creator 3)]) ; set up the chooser
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(for ([d (in-vector ; iterate over the chosen digits
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(for/last ([digit (in-range 0 10)]) ; loop through the digits
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(s-of-n digit)))]) ; feed them in
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(hash-update! counts d add1)))) ; update counts
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(for ([d (in-range 0 10)])
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(printf "~a ~a~n" d (hash-ref counts d)))
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