50 lines
1.3 KiB
Racket
50 lines
1.3 KiB
Racket
#lang curly-fn racket
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(require "scripts/aoc.rkt")
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;; solution for day 13
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(define (<=> l r)
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(cond
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[(= l r) 0]
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[(< l r) -1]
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[else 1]))
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(define (cmp l r)
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(match* (l r)
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[(_ (? integer?)) (cmp l (list r))]
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[((? integer?) _) (cmp (list l) r)]
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[('() '()) 0]
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[((list* lf lr) '()) 1]
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[('() (list* rf rr)) -1]
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[((list* (? integer? lf) lr) (list* (? integer? rf) rr))
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(match (<=> lf rf)
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[0 (cmp lr rr)]
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[x x])]
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[((list* lf lr) (list* rf rr))
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(match (cmp lf rf)
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[0 (cmp lr rr)]
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[x x])]))
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(define (part1 input)
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(for/sum ([pair (in-list input)] [idx (in-naturals 1)]
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#:when (= -1 (cmp (first pair) (second pair))))
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idx))
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(define (part2 input)
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(define special '(((2)) ((6))))
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(define sorted (sort (apply append special input) #{= -1 (cmp %1 %2)}))
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(~>> special (map #{index-of sorted %}) (map add1) (apply *)))
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(define (parse fname)
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(define (parse-line line)
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(read (open-input-string (string-replace line "," " "))))
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(for/list ([pair-str (in-list (string-split (file->string fname) "\n\n"))])
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(map parse-line (string-split pair-str "\n"))))
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(module+ main
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(define input (parse "inputs/13"))
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(answer 13 1 (time (part1 input)))
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(answer 13 2 (time (part2 input)))
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(displayln "meow"))
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