25 lines
634 B
Racket
25 lines
634 B
Racket
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#lang curly-fn racket
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(require "../lib.rkt")
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(define input (sort (map string->number (problem-input 10)) <=))
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(define part1
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(let* ([input (cons 0 input)]
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[diffs (for/list ([i (rest input)] [j input]) (- i j))]
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[ones (count #{= % 1} diffs)]
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[threes (add1 (count #{= % 3} diffs))])
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(* ones threes)))
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(define arrangements
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(for*/fold ([arrs (hash 0 1)])
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([joltage input]
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[i (range 1 4)])
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(let ([prev (hash-ref arrs (- joltage i) 0)])
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(hash-update arrs joltage #{+ % prev} 0))))
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(define part2
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(hash-ref arrangements (last input)))
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(show-solution part1 part2)
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