49 lines
1.2 KiB
Racket
49 lines
1.2 KiB
Racket
#lang racket
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(module+ test
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(require rackunit))
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(module+ main
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(displayln "Day 10"))
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(define (read-input filename)
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(define input (map string->number (file->lines filename)))
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(sort (cons 0 (cons (target input) input)) <))
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(define (target lst)
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(+ 3 (apply max lst)))
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(define (part1 filename)
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(define jolts (read-input filename))
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(define counts (make-hash))
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(for ([x (in-list (drop jolts 1))]
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[y (in-list jolts)])
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(hash-update! counts (- x y) add1 0))
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(* (hash-ref counts 1 0) (hash-ref counts 3 0)))
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(module+ test
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(check-equal? (part1 "test1") (* 7 5))
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(check-equal? (part1 "test2") (* 22 10)))
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(module+ main
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(displayln (part1 "input")))
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(define (count-paths jolts)
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(define counts (make-hash))
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(hash-set! counts 0 1)
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(for ([x (in-list (cdr jolts))])
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(hash-set! counts x (+ (hash-ref counts (- x 1) 0)
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(hash-ref counts (- x 2) 0)
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(hash-ref counts (- x 3) 0))))
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(hash-ref counts (last jolts)))
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(define (part2 filename)
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(define jolts (read-input filename))
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(count-paths jolts))
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(module+ test
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(check-equal? (part2 "test1") 8)
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(check-equal? (part2 "test2") 19208))
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(module+ main
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(displayln (part2 "input")))
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