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#lang racket
(require racket/struct
advent-of-code
fancy-app
relation
threading
rebellion/base/range)
(struct field-rule (name range1 range2) #:transparent)
(define (make-lines strs)
(string-split strs "\n"))
(define (seperate-fields strs)
(~>> (string-split strs ",") (map ->number)))
(define (process-rules str)
(match str
[(regexp
#px"(.+): (\\d+)-(\\d+) or (\\d+)-(\\d+)"
(list _ name (app ->number min1) (app ->number max1) (app ->number min2) (app ->number max2)))
(field-rule name (closed-range min1 max1) (closed-range min2 max2))]))
(match-define (list (app (λ~>> make-lines (map process-rules)) ticket-rules)
(app (λ~>> make-lines second seperate-fields) your-ticket)
(app (λ~>> make-lines rest (map seperate-fields)) other-tickets))
(~> (fetch-aoc-input (find-session) 2020 16 #:cache #true) (string-split "\n\n")))
;; part 1
(define (fails-all-checks? field rules)
(define rule-list (~>> rules (map (λ~> struct->list rest)) flatten))
(for/and ([rule (in-list rule-list)])
(not (range-contains? rule field))))
(define (ticket-scanning-error-rate tickets rules)
(for*/sum
([ticket (in-list tickets)] (field (in-list ticket)) #:when (fails-all-checks? field rules))
field))
(ticket-scanning-error-rate other-tickets ticket-rules)
;; part 2
(define valid-tickets (filter (ormap (fails-all-checks? _ ticket-rules) _) other-tickets))
(define fields (apply map list valid-tickets))
(for/list ([field (in-list fields)])
(for*/list (
[rule (in-list ticket-rules)]
#:unless (not (or (range-contains? (field-rule-range1 rule) value)
(range-contains? (field-rule-range2 rule) value))))
(field-rule-name rule)))
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