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60 lines
1.9 KiB
Racket
60 lines
1.9 KiB
Racket
#lang br/quicklang
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(module+ reader (provide read-syntax))
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(define (read-syntax path port)
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(strip-bindings
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#`(module mod "day07.rkt"
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#,@(for/list ([ip (in-lines port)]
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#:when (not (equal? ip "")))
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ip))))
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(provide (rename-out [mb #%module-begin]))
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(define-macro (mb . IPS)
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#'(#%module-begin
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(define ips (list . IPS))
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(displayln (format "part a: ~a" (length (filter supports-tls? ips))))
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(displayln (format "part b: ~a" (length (filter supports-ssl? ips))))))
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(define bracketed-pattern #rx"\\[.*?\\]")
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(define (bracketed-parts str)
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(regexp-match* bracketed-pattern str))
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(define (unbracketed-parts str)
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(string-split str bracketed-pattern))
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(define (has-abba? str)
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(for*/or ([idx (in-range (string-length str))]
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[substr (in-list (regexp-match* #px"^\\w\\w\\w\\w" str idx))]
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#:when substr)
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(define cs (string->list substr))
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(and
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(char=? (first cs) (fourth cs))
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(char=? (second cs) (third cs))
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(not (char=? (first cs) (second cs))))))
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(define (supports-tls? str)
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(and
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(ormap has-abba? (unbracketed-parts str))
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(andmap (negate has-abba?) (bracketed-parts str))))
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(define (find-abas str)
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(for*/list ([idx (in-range (string-length str))]
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[substr (in-list (regexp-match* #px"^\\w\\w\\w" str idx))]
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[cs (in-value (string->list substr))]
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#:when (and
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substr
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(char=? (first cs) (third cs))
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(not (char=? (first cs) (second cs)))))
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substr))
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(define (aba->bab aba) (format "~a~a~a" (substring aba 1 2)
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(substring aba 0 1)
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(substring aba 1 2)))
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(define (supports-ssl? str)
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(define abas (append-map find-abas (unbracketed-parts str)))
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(for*/or ([bab (in-list (map aba->bab abas))]
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[str (in-list (bracketed-parts str))])
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(regexp-match bab str)))
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