74 lines
2.1 KiB
Racket
74 lines
2.1 KiB
Racket
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#lang racket
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(require data/queue
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graph
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(except-in "../lib.rkt" transpose))
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(define input
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(problem-input 18))
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(define list-grid
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(map string->list input))
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(define vector-grid
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(lists->vectors list-grid))
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(define width
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(length (car list-grid)))
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(define height
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(length list-grid))
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(define (get-char coord)
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(match-let ([(list x y) coord])
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(if (or (< x 0) (< y 0)
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(>= x width)
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(>= y height))
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#\#
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(vector-ref (vector-ref vector-grid y) x))))
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(define (neighbours coord)
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(match-let ([(list x y) coord])
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(let ([U (list x (sub1 y))]
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[D (list x (add1 y))]
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[L (list (sub1 x) y)]
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[R (list (add1 x) y)])
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(filter-not
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(∘ (∂ char=? #\#) (∂ get-char))
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(list U D L R)))))
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(define key-door-graph
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(let* ([Q (make-queue)]
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[entrance (list (round (/ width 2))
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(round (/ height 2)))]
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[visited (make-hash `((,entrance . #t)))]
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[graph (weighted-graph/undirected '())])
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(enqueue! Q (list entrance #\@ 0))
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(let loop ()
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(if (queue-empty? Q)
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graph
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(match-let* ([(list coord prev dist) (dequeue! Q)]
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[ncoords (neighbours coord)])
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(for-each
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(λ (ncoord)
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(let ([nc (get-char ncoord)])
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(cond
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[(hash-ref visited ncoord #f)]
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[(char=? #\. nc)
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(hash-set! visited ncoord #t)
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(enqueue! Q (list ncoord prev (add1 dist)))]
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[else
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(hash-set! visited ncoord #t)
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(enqueue! Q (list ncoord nc 0))
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(add-edge! graph prev nc (add1 dist))])))
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ncoords)
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(loop))))))
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(define ordered-keys
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(let ([keys (filter char-lower-case? (get-vertices key-door-graph))])
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(displayln keys)
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(define (sort-fn c1 c2)
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(not (member (char-upcase c2) (fewest-vertices-path key-door-graph #\@ c1))))
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(sort keys sort-fn)))
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#;(for-each displayln (map (λ (s) (string-replace (string-replace s "#" "█") "." " ")) input))
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