85 lines
2.7 KiB
Racket
85 lines
2.7 KiB
Racket
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#lang curly-fn racket
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(require "scripts/aoc.rkt")
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;; solution for day 16
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(struct note [name rule0 rule1] #:transparent)
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(define (invalid? notes val)
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(not
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(for/or ([n (in-list notes)])
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(match-define (note name (cons a b) (cons c d)) n)
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(or (and (>= val a) (<= val b)) (and (>= val c) (<= val d))))))
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(define (part1 input)
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(match-define (list notes yours others) input)
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(for/sum ([tick (in-list others)])
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(for/sum ([val (in-list tick)] #:when (invalid? notes val)) val)))
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(define (part2 input)
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(match-define (list notes yours others) input)
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(define (ticket-valid? tick)
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(not (for/or ([val (in-list tick)]) (invalid? notes val))))
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(define valid-tickets (filter ticket-valid? others))
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(define mapping (make-hash))
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(for ([idx (in-range (length yours))])
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(define decided-note (mutable-set))
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(for ([cand-note (in-list notes)])
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(define shonks
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(for/and ([tick (in-list valid-tickets)])
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(not (invalid? (list cand-note) (list-ref tick idx)))))
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(when shonks
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(set-add! decided-note (note-name cand-note))))
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(when (set-empty? decided-note) (error "couldn't decide..."))
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(hash-set! mapping idx decided-note))
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; (displayln mapping)
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(let loop ()
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(for ([(k v) (in-hash mapping)])
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(when (= 1 (set-count v))
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(define fst (set-first v))
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(for ([k2 (in-list (hash-keys mapping))] #:unless (= k2 k))
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(set-remove! (hash-ref mapping k2) fst))))
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(when (for/or ([(k v) (in-hash mapping)])
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(> (set-count v) 1))
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(displayln "looping")
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(loop)))
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(displayln mapping)
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(for/product ([val (in-list yours)] [idx (in-naturals)])
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(define n (set-first (hash-ref mapping idx)))
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(displayln n)
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(if (string-contains? n "departure")
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(begin (displayln val) val)
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1)))
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;; parse input file
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(define (parse fname)
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(match-define (list notes yours others) (string-split (file->string fname) "\n\n"))
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(define sn string->number)
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(define pnotes (for/list ([line (in-list (string-split notes "\n"))])
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(match line
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[(pregexp #px"^([^:]+): (\\d+)\\-(\\d+) or (\\d+)-(\\d+)$"
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(list _ name a b c d))
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(note name (cons (sn a) (sn b)) (cons (sn c) (sn d)))])))
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(define pyours (map sn (string-split (second (string-split yours "\n")) ",")))
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(define pothers (for/list ([line (in-list (rest (string-split others "\n")))])
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(map sn (string-split line ","))))
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(list pnotes pyours pothers))
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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/16"))
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(answer 16 1 (time (part1 input)))
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(answer 16 2 (time (part2 input)))
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(displayln "meow"))
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