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18 lines
461 B
Racket
18 lines
461 B
Racket
4 years ago
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#lang br
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(require racket/file srfi/13 rackunit)
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(define (seat-id seat)
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(for/sum ([(c i) (in-indexed (string-reverse seat))]
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#:when (memv c '(#\R #\B)))
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(arithmetic-shift 1 i)))
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(define seat-ids (map seat-id (file->lines "05.rktd")))
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(check-equal? (apply max seat-ids) 915)
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(check-equal?
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(for/first ([first (sort seat-ids <)]
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[second (cdr (sort seat-ids <))]
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#:when (= 2 (- second first)))
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(sub1 second))
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699)
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