77 lines
2.7 KiB
Racket
77 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 5
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(struct rngmap [dst src len] #:transparent)
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(define (transform-layer num mapping)
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(or
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(for/first ([entry (in-list mapping)]
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#:do [(match-define (rngmap dst src len) entry)]
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#:when (>= num src)
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#:when (< num (+ src len)))
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(+ dst (- num src)))
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num))
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(define (transform-all num mappings)
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(for/fold ([cur-num num]) ([mapping (in-list mappings)])
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(transform-layer cur-num mapping)))
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(define (part1 input)
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(apply min
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(for/list ([num (in-list (first input))])
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(transform-all num (rest input)))))
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(define (part2-transform-layer iset mapping)
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(define-values [rem-src dst]
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(for/fold ([cur-src iset] [cur-dst (is:make-integer-set '())])
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([entry (in-list mapping)]
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#:do [(match-define (rngmap dst src len) entry)])
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(define entry-src (is:make-range src (+ src (sub1 len))))
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(define captured-values (is:intersect cur-src entry-src))
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(define captured-wfs (is:integer-set-contents captured-values))
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(define transformed-wfs
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(for/list ([wfs-entry (in-list captured-wfs)])
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(cons (+ dst (- (car wfs-entry) src))
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(+ dst (- (cdr wfs-entry) src)))))
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(define transformed-iset (is:make-integer-set transformed-wfs))
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(values (is:subtract cur-src entry-src) (is:union cur-dst transformed-iset))))
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(is:union rem-src dst))
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(define (part2-transform-all iset mappings)
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(for/fold ([cur-iset iset]) ([mapping (in-list mappings)])
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(part2-transform-layer cur-iset mapping)))
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(define (part2 input)
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(define ranges (first input))
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(define ranges-iset
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(for/fold ([is (is:make-integer-set '())])
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([chunk (in-slice 2 (in-list ranges))])
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(is:union is
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(is:make-range (first chunk) (+ (first chunk) (sub1 (second chunk)))))))
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(define mappings (rest input))
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(define ranges-out (part2-transform-all ranges-iset mappings))
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(car (first (is:integer-set-contents ranges-out))))
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(define (parse fname)
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(match-define (cons initial mappings) (string-split (file->string fname) "\n\n"))
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(define initial-nums (map string->number (rest (string-split initial " "))))
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(define mapping-nums
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(for/list ([map-str (in-list mappings)])
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(define entries (rest (string-split map-str "\n")))
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(for/list ([entry (in-list entries)])
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(match-define (list dst src len) (map string->number (string-split entry " ")))
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(rngmap dst src len))))
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(cons initial-nums mapping-nums))
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; (part2 (parse "inputs/5-test1"))
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; (error)
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(module+ main
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(define input (parse "inputs/5"))
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(answer 5 1 (time (part1 input)))
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(answer 5 2 (time (part2 input)))
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(displayln "meow"))
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