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#lang br/quicklang
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(require openssl/md5)
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(define (read-syntax path port)
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(strip-bindings
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#`(module mod "day05.rkt"
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(solve #,(string-trim (port->string port))))))
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(module+ reader (provide read-syntax))
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(provide #%module-begin)
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(define (solve key)
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(define-values
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(part-a-solution part-b-solution)
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(for*/fold ([part-a empty]
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[part-b (make-vector 8 #f)])
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([idx (in-naturals 1000000)]
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[this-key (in-value (format "~a~a" key idx))]
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#:break (and (= 8 (length part-a))
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(andmap string? (vector->list part-b))))
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(define this-hash (md5 (open-input-string this-key)))
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(define next-part-a
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(if (and (not (= 8 (length part-a)))
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(string-prefix? this-hash "00000"))
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(let ([next-str (substring this-hash 5 6)])
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(displayln (format "part a progress: ~a" next-str))
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(cons next-str part-a))
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part-a))
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(define next-part-b
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(let ()
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(when (and (string-prefix? this-hash "00000")
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(string->number (substring this-hash 5 6))
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(<= 0 (string->number (substring this-hash 5 6)) 7)
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(not (vector-ref part-b (string->number (substring this-hash 5 6)))))
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(displayln (format "part b progress: idx ~a, hash ~a, ~a at ~a" idx this-hash (substring this-hash 6 7) (substring this-hash 5 6)))
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(vector-set! part-b (string->number (substring this-hash 5 6)) (substring this-hash 6 7)))
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part-b))
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(values next-part-a next-part-b)))
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(displayln (format "part a: ~a" (apply string-append (reverse part-a-solution))))
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(displayln (format "part b: ~a" (apply string-append (vector->list part-b-solution)))))
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(provide solve)
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