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34 lines
1.2 KiB
Racket
34 lines
1.2 KiB
Racket
5 years ago
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#lang br
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(require racket/file rackunit racket/set graph)
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(define str (file->string "20.rktd"))
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(define (find-cells pred)
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(for*/hasheqv ([(row ridx) (in-indexed (string-split str "\n"))]
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[(c cidx) (in-indexed row)]
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#:when (pred c))
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(values (make-rectangular cidx ridx) c)))
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(define passage-locs (find-cells (λ (c) (char=? c #\.))))
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(define letter-locs (find-cells char-alphabetic?))
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(define g (unweighted-graph/undirected null))
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(for* ([loc (in-hash-keys passage-locs)]
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[delta (list 1 -1 +i -i)])
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(when (hash-has-key? passage-locs (+ loc delta))
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(add-edge! g loc (+ loc delta)))
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(when (hash-has-key? letter-locs (+ loc delta))
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(add-edge! g loc (string->symbol
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(apply string ((if (member delta (list -1 -i))
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reverse
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values) (for/list ([d (list delta (* 2 delta))])
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(hash-ref letter-locs (+ loc d)))))))))
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(for ([v (in-vertices g)]
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#:when (and (symbol? v) (not (memq v '(AA ZZ)))))
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(apply add-edge! g (get-neighbors g v)))
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;; 1
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(check-eq? (- (length (fewest-vertices-path g 'AA 'ZZ)) 3) 638)
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