81 lines
2.5 KiB
Racket
81 lines
2.5 KiB
Racket
#lang curly-fn racket
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(require "scripts/aoc.rkt")
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;; solution for day 14
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(define (part1 input)
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(define (parse-mask msk)
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(define orval (for/fold ([val 0]) ([chr (in-string msk)])
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(+ (* val 2) (if (equal? chr #\1) 1 0))))
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(define andval (for/fold ([val 0]) ([chr (in-string msk)])
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(+ (* val 2) (if (equal? chr #\0) 0 1))))
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(values orval andval))
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(define orval 0)
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(define andval (sub1 (expt 2 37)))
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(define mem (make-hash))
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(for ([ins (in-list input)])
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(match ins
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[(cons 'mask mask)
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(define-values [ov av] (parse-mask mask))
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(set! orval ov) (set! andval av)]
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[(cons 'set (cons addr val))
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(define new-val (bitwise-ior (bitwise-and val andval) orval))
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(hash-set! mem addr new-val)]))
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(for/sum ([(k v) (in-hash mem)])
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v))
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(define (addr->bits addr)
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(vector-copy
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(for/vector ([i (in-range 36)])
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(bitwise-and 1 (arithmetic-shift addr (+ -35 i))))))
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(define (bits->addr bits)
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(for/fold ([val 0]) ([bit (in-vector bits)])
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(+ (* val 2) bit)))
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(define (part2 input)
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(define mem (make-hash))
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(define mask #f)
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(for ([ins (in-list input)])
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(match ins
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[(cons 'mask m) (set! mask m)]
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[(cons 'set (cons addr val))
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(define addr-bits (addr->bits addr))
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(for ([chr (in-string mask)] [i (in-naturals)])
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(when (equal? chr #\1)
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(vector-set! addr-bits i 1)))
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(define addrs-set (list addr-bits))
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(for ([chr (in-string mask)] [i (in-naturals)])
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(when (equal? chr #\X)
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(define ones (map (lambda (x) (define y (vector-copy x)) (vector-set! y i 1) y)
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addrs-set))
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(define zeros (map (lambda (x) (define y (vector-copy x)) (vector-set! y i 0) y)
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addrs-set))
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(set! addrs-set (append ones zeros))))
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(for ([addr (in-list addrs-set)])
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(hash-set! mem (bits->addr addr) val))]))
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(for/sum ([(k v) (in-hash mem)])
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v))
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;; parse input file
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(define (parse fname)
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(define input (file->lines fname))
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(for/list ([i (in-list input)])
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(match i
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[(pregexp #px"^mask = (.*?)$" (list _ mask)) (cons 'mask mask)]
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[(pregexp #px"^mem\\[([0-9]+)\\] = ([0-9]+)$" (list _ addr val))
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(cons 'set (cons (string->number addr) (string->number val)))]
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[_ (error "not shonks i")])))
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(module+ test
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(require rackunit)
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;; tests here
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(displayln "no tests :("))
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(module+ main
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(define input (parse "inputs/14"))
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(answer 14 1 (time (part1 input)))
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(answer 14 2 (time (part2 input)))
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(displayln "meow"))
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