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60 lines
2.3 KiB
Racket
60 lines
2.3 KiB
Racket
4 years ago
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#lang br
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(require racket/file rackunit)
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(match-define (list fields my-ticket other-tickets)
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(string-split (file->string "16.rktd") "\n\n"))
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(struct predicate (name func) #:transparent)
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(define predicates
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(for/list ([field (string-split fields "\n")])
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(match (regexp-match #px"^(.*?): (\\d+)-(\\d+) or (\\d+)-(\\d+)$" field)
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[(list* _ name numstrs)
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(match-define (list val1 val2 val3 val4) (map string->number numstrs))
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(predicate name (λ (x) (or (<= val1 x val2) (<= val3 x val4))))])))
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(define (t2intvec t) (list->vector (map string->number (string-split t ","))))
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(check-equal? (for*/sum ([ticket (cdr (string-split other-tickets "\n"))]
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[intvec (t2intvec ticket)]
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#:unless (for/or ([pred predicates])
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((predicate-func pred) intvec)))
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intvec) 26988)
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(define all-tickets (cdr (string-split other-tickets "\n")))
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(define (ticket-valid? ticket)
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(for/and ([intvec (t2intvec ticket)])
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(for/or ([pred predicates])
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((predicate-func pred) intvec))))
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(define valid-tickets (filter ticket-valid? all-tickets))
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(define-values (departure-predicates other-predicates)
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(partition (λ (p) (string-prefix? (predicate-name p) "departure")) predicates))
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(define winning-idxss
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(let loop ([extra-count 0])
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(define predicates-to-test
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(append departure-predicates (take other-predicates extra-count)))
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(define possible-winning-idxss
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(let ([valid-ticket-vecs (map t2intvec valid-tickets)])
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(for/list ([idxs (in-combinations (range (length predicates))
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(length predicates-to-test))]
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#:when (for/and ([intvec valid-ticket-vecs])
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(for/and ([idx idxs]
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[pred departure-predicates])
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((predicate-func pred) (vector-ref intvec idx)))))
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idxs)))
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(match possible-winning-idxss
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[(list winner) (drop-right winner extra-count)]
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[_ (loop (add1 extra-count))])))
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;; too many possibilities
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winning-idxss
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#;(define my-ticket-intvec (t2intvec (cadr (string-split my-ticket "\n"))))
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#;(for/product ([idx winning-idxs]
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[pred departure-predicates])
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(vector-ref my-ticket-intvec idx))
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