37 lines
1.0 KiB
Racket
37 lines
1.0 KiB
Racket
#lang curly-fn racket
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(require "scripts/aoc.rkt")
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;; solution for day 8
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(define (part1 input [cur "AAA"] [break? #{equal? % "ZZZ"}])
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(for/fold ([cur cur] [cnt 0] #:result cnt)
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([inst (in-cycle (in-list (first input)))])
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#:break (break? cur)
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(values (inst (hash-ref (second input) cur))
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(add1 cnt))))
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(define (part2 input)
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(~> (filter #{string-suffix? % "A"}
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(hash-keys (second input)))
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(map #{part1 input % #{string-suffix? % "Z"}} _)
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(apply lcm _)))
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(define (parse fname)
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(match-define (list* instl _ mapl) (file->lines fname))
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(list
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(for/list ([c (in-string instl)])
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(match c
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[#\L first]
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[#\R second]))
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(for/hash ([line (in-list mapl)])
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(match-define (list node left right)
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(regexp-match* #px"[A-Z0-9]{3}" line))
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(values node (list left right)))))
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(module+ main
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(define input (parse "inputs/8"))
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(answer 8 1 (time (part1 input)))
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(answer 8 2 (time (part2 input)))
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(displayln "meow"))
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