26 lines
837 B
Racket
26 lines
837 B
Racket
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#lang racket
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(require "../lib.rkt")
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(define (string->rc str)
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(let* ([row-str (substring str 0 7)]
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[col-str (substring str 7 10)]
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[as-binary (∘ string->number (∂ string-append "#b"))]
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[row (as-binary (regexp-replaces row-str '([#rx"F" "0"] [#rx"B" "1"])))]
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[col (as-binary (regexp-replaces col-str '([#rx"L" "0"] [#rx"R" "1"])))])
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(cons row col)))
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(define input (map string->rc (problem-input 5)))
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(define part1
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(apply max (map (match-lambda [`(,row . ,col) (+ (* row 8) col)]) input)))
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(define part2
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(let ([grid (make-vector-grid 8 128 #\o)])
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(for ([rc input])
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(vector-grid-update grid rc #\x))
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(let ([str (apply string-append (map list->string (vectors->lists grid)))])
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(add1 (car (first (regexp-match-positions #rx"xox" str)))))))
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(show-solution part1 part2)
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