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53 lines
1.5 KiB
Racket
53 lines
1.5 KiB
Racket
3 years ago
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#lang br
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(require racket/file rackunit)
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(define (make-octopodes)
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(define octopodes (make-hasheqv))
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(for* ([(line lidx) (in-indexed (file->lines "11.rktd"))]
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[(depth cidx) (in-indexed line)])
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(hash-set! octopodes (make-rectangular cidx lidx) (string->number (string depth))))
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octopodes)
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(define octopodes (make-octopodes))
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(define (neighbors loc)
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(remove loc
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(for*/list ([rd '(-1 0 1)]
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[id '(-1 0 1)])
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(+ loc (make-rectangular rd id)))))
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(define (increment! loc)
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(cond
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[(number? (hash-ref octopodes loc #false))
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(define next-val
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(match (modulo (add1 (hash-ref octopodes loc)) 10)
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[0 'flashed]
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[val val]))
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(hash-set! octopodes loc next-val)
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(when (eq? next-val 'flashed)
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(for-each increment! (neighbors loc)))]))
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(define (find-flashes-and-reset)
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(for/list ([(loc val) (in-hash octopodes)]
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#:when (eq? val 'flashed))
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(hash-set! octopodes loc 0)
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loc))
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(define (part-1)
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(for/fold ([flashes null]
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#:result (length flashes))
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([step (in-range 100)])
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(for-each increment! (hash-keys octopodes))
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(append (find-flashes-and-reset) flashes)))
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(check-equal? (part-1) 1705)
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(set! octopodes (make-octopodes))
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(define (part-2)
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(for/or ([step (in-naturals)])
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(for-each increment! (hash-keys octopodes))
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(and (= (length (find-flashes-and-reset)) (length (hash-keys octopodes))) (add1 step))))
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(check-equal? (part-2) 265)
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