61 lines
1.5 KiB
Racket
61 lines
1.5 KiB
Racket
#lang racket
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(module+ test
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(require rackunit))
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(module+ main
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(displayln "Day 2"))
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(struct policy
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(lower upper char)
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#:transparent)
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(define (parse-line str)
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(define lst (string-split str #px"(\\s+|:\\s+|-)"))
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(values (policy (string->number (first lst))
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(string->number (second lst))
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(car (string->list (third lst))))
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(last lst)))
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(define (read-input filename)
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(with-input-from-file filename
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(lambda ()
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(for/lists (policies passwords)
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([line (in-lines)])
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(parse-line line)))))
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(define (valid? pol pass)
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(define cnt (count (λ (x) (equal? x (policy-char pol)))
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(string->list pass)))
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(and (<= (policy-lower pol) cnt)
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(>= (policy-upper pol) cnt)))
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(define (part1 filename)
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(define-values (policies passwords) (read-input filename))
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(for/sum ([pol policies]
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[pass passwords]
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#:when (valid? pol pass))
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1))
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(module+ test
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(check-equal? (part1 "test") 2))
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(module+ main
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(displayln (part1 "input")))
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(define (new-valid? pol pass)
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(xor (equal? (string-ref pass (sub1 (policy-lower pol))) (policy-char pol))
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(equal? (string-ref pass (sub1 (policy-upper pol))) (policy-char pol))))
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(define (part2 filename)
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(define-values (policies passwords) (read-input filename))
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(for/sum ([pol policies]
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[pass passwords]
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#:when (new-valid? pol pass))
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1))
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(module+ test
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(check-equal? (part2 "test") 1))
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(module+ main
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(displayln (part2 "input")))
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