82 lines
2.3 KiB
Racket
82 lines
2.3 KiB
Racket
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#lang plai
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(require "../lib.rkt"
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"IntCode.rkt")
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(define input
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(string->program (car (problem-input 11))))
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;; The hull as a hash (x . y) -> c
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;; x increases rightward
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;; y increases downward
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(define hull (make-hash))
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;; The hull as a vector of row vectors of c
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;; i.e. x = index of inner vectors,
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;; y = index of outer vector
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(define (make-grid xrange yrange)
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(build-vector
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(add1 yrange)
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(λ (_) (make-vector (add1 xrange) #\ ))))
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;; Turn CCW if δ = 0, CW if δ = 1
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(define (update-dir dir δ)
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(match dir
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['U (if (zero? δ) 'L 'R)]
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['D (if (zero? δ) 'R 'L)]
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['L (if (zero? δ) 'D 'U)]
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['R (if (zero? δ) 'U 'D)]))
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;; Move in given direction (up/down/left/right)
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(define (update-pos dir xy)
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(let ([x (car xy)]
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[y (cdr xy)])
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(match dir
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['U (cons x (sub1 y))]
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['D (cons x (add1 y))]
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['L (cons (sub1 x) y)]
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['R (cons (add1 x) y)])))
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;; Deploy the emergency hull painting robot!
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(define (deploy st dir xy)
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(define clr (hash-ref hull xy 0))
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(type-case state st
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[halt (_) (void)]
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[in (resume)
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(let*-values
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([(clr* st) (resume-with-output (resume clr))]
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[(δ st) (resume-with-output st)])
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(cond [(neq? clr clr*)
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(hash-set! hull xy clr*)])
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(let* ([dir (update-dir dir δ)]
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[xy (update-pos dir xy)])
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(deploy st dir xy)))]
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[else (error "Unexpected program state.")]))
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(define (part1)
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(deploy (exec input) 'U '(0 . 0))
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(hash-count hull))
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(define (part2)
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(set! hull (make-hash '(((0 . 0) . 1))))
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(deploy (exec input) 'U '(0 . 0))
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(let* ([positions (hash-keys hull)]
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[xs (map car positions)]
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[ys (map cdr positions)]
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[xmin (apply min xs)] [xmax (apply max xs)]
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[ymin (apply min ys)] [ymax (apply max ys)]
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[xrange (- xmax xmin)] [yrange (- ymax ymin)]
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[grid (make-grid xrange yrange)])
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(for-each
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(λ (kv)
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(let* ([x (- (caar kv) xmin)]
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[y (- (cdar kv) ymin)]
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[c (cdr kv)]
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[row (vector-ref grid y)])
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(cond [(= c 1) (vector-set! row x #\█)])))
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(hash->list hull))
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(for-each
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(λ (row) (displayln (list->string (vector->list row))))
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(vector->list grid))))
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(show-solution (part1) (part2))
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