61 lines
1.5 KiB
Racket
61 lines
1.5 KiB
Racket
#lang curly-fn racket
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(require "scripts/aoc.rkt")
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;; solution for day 10
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;; helper functions here
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(define (part1 input)
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(define sorted (sort input <))
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(define-values [_ ones threes]
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(for/fold ([prev 0] [ones 0] [threes 0]) ([x (in-list sorted)])
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(values x (+ ones (if (= 1 (- x prev)) 1 0))
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(+ threes (if (= 3 (- x prev)) 1 0)))))
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(* ones (add1 threes)))
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(define (part2 input)
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(define is (cons 0 (sort input <)))
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(define-values [edges _]
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(for/fold ([edges '()] [lst (rest is)]) ([x (in-list is)])
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(define res3
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(if (and (> (length lst) 2) (<= (- (third lst) 3) x))
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(list (list x (third lst)))
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'()))
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(define res2
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(if (and (> (length lst) 1) (<= (- (second lst) 3) x))
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(list (list x (second lst)))
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'()))
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(define res1
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(if (and (> (length lst) 0) (<= (- (first lst) 3) x))
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(list (list x (first lst)))
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'()))
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(values (append edges res1 res2 res3) (if (empty? lst) '() (rest lst)))))
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(define G (directed-graph edges))
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(define wanted (last is))
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(define/memoized (count-paths node)
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(cond [(= node wanted) 1]
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[else (for/sum ([x (in-neighbors G node)])
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(count-paths x))]))
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(count-paths 0))
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(module+ test
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(require rackunit)
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(check-equal?
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8 (part2
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'(16 10 15 5 1 11 7 19 6 12 4))))
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(module+ main
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(define input (map string->number (file->lines "inputs/10")))
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;; part 1
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(answer 10 1 (part1 input))
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;; part 2
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(answer 10 2 (part2 input))
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(displayln "meow"))
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