86 lines
2.7 KiB
Racket
86 lines
2.7 KiB
Racket
#lang curly-fn racket
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(require "scripts/aoc.rkt")
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;; solution for day 23
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;; this doesn't noticably change execution time :(
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; (require racket/unsafe/ops)
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; (define-simple-macro (mcar x) (unsafe-mcar x))
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; (define-simple-macro (mcdr x) (unsafe-mcdr x))
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; (define-simple-macro (set-mcar! l x) (unsafe-set-mcar! l x))
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; (define-simple-macro (set-mcdr! l x) (unsafe-set-mcdr! l x))
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; (define-simple-macro (vector-ref v i) (unsafe-vector-ref v i))
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; (define-simple-macro (= a b) (unsafe-fx= a b))
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; (define-simple-macro (sub1 x) (unsafe-fx- x 1))
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; (define-simple-macro (zero? x) (unsafe-fx= x 0))
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(define (move-opt* input times)
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(define total (vector-length input))
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(define-values [total+ total-] (values (add1 total) (sub1 total)))
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(define items-map
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(for/vector ([i (in-range total+)])
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(if (zero? i) #f (mcons i #f))))
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;; wrap it
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(define fst (vector-ref items-map (vector-ref input 0)))
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(define lst (vector-ref items-map (vector-ref input total-)))
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(set-mcdr! lst fst)
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;; fill in the rest
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(for ([i (in-range 1 total)])
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(set-mcdr! (vector-ref items-map (vector-ref input (sub1 i)))
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(vector-ref items-map (vector-ref input i))))
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(for/fold ([item-ref fst]) ([i (in-range times)])
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(define current (mcar item-ref))
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;; 🦈
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(define top (mcdr item-ref))
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(define mid (mcdr top))
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(define bottom (mcdr mid))
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;; the card values, for comparison against the card number to insert after
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(define-values [tv mv bv] (values (mcar top) (mcar mid) (mcar bottom)))
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;; unlink
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(set-mcdr! item-ref (mcdr bottom))
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(define wanted-value
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(let loop ([wanted (sub1 current)])
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(cond [(zero? wanted) (loop total)]
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[(or (= wanted tv) (= wanted mv) (= wanted bv))
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(loop (sub1 wanted))]
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[else wanted])))
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;; relink in new place
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(define wanted-ref (vector-ref items-map wanted-value))
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(set-mcdr! bottom (mcdr wanted-ref))
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(set-mcdr! wanted-ref top)
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;; return next head ref
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(mcdr item-ref))
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(vector-ref items-map 1))
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(define (part1 input)
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(define res (move-opt* input 100))
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(let loop ([x (mcdr res)])
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(if (eq? x res)
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""
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(string-append (number->string (mcar x)) (loop (mcdr x))))))
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(define (part2 input)
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(define rst (for/vector ([x (in-range (add1 (vector-length input)) 1000001)]) x))
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(define all (vector-append input rst))
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(define res (move-opt* all 10000000))
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(* (mcar (mcdr (mcdr res))) (mcar (mcdr res))))
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;; parse input file
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(define (parse fname)
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(~>> fname file->string (regexp-match* #px"\\d") (map string->number) list->vector))
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(module+ main
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(define input (parse "inputs/23"))
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(answer 23 1 (time (part1 input)))
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(answer 23 2 (time (part2 input)))
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(displayln "meow"))
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