finish day07

2016
Matthew Butterick 7 years ago
parent fe604327c1
commit 1c97c199b0

@ -11,14 +11,49 @@
(provide (rename-out [mb #%module-begin]))
(define-macro (mb . IPS)
#'(#%module-begin
(length (filter supports-tls? (list . IPS)))
(map supports-tls? (list . IPS))))
(define ips (list . IPS))
(displayln (format "part a: ~a" (length (filter supports-tls? ips))))
(displayln (format "part b: ~a" (length (filter supports-ssl? ips))))))
(define (supports-tls? x)
(define bracketed-pattern #rx"\\[.*?\\]")
(define (bracketed-parts str)
(regexp-match* bracketed-pattern str))
(define (unbracketed-parts str)
(string-split str bracketed-pattern))
(define (has-abba? str)
(for*/or ([idx (in-range (string-length str))]
[substr (in-list (regexp-match* #px"^\\w\\w\\w\\w" str idx))]
#:when substr)
(define cs (string->list substr))
(and
(char=? (first cs) (fourth cs))
(char=? (second cs) (third cs))
(not (char=? (first cs) (second cs))))))
(define (supports-tls? str)
(and
(let ([maybe-abbas (regexp-match* #px"(\\w)(\\w)\\2\\1" x)])
(ormap (λ(ma)
(not (equal? (substring ma 0 1) (substring ma 1 2)))) maybe-abbas))
(let ([maybe-bad-abbas (regexp-match* #px"\\[.*((\\w)(\\w)\\3\\2).*\\]" x #:match-select cadr)])
(andmap (λ(ma)
(equal? (substring ma 0 1) (substring ma 1 2))) maybe-bad-abbas))))
(ormap has-abba? (unbracketed-parts str))
(andmap (negate has-abba?) (bracketed-parts str))))
(define (find-abas str)
(for*/list ([idx (in-range (string-length str))]
[substr (in-list (regexp-match* #px"^\\w\\w\\w" str idx))]
[cs (in-value (string->list substr))]
#:when (and
substr
(char=? (first cs) (third cs))
(not (char=? (first cs) (second cs)))))
substr))
(define (aba->bab aba) (format "~a~a~a" (substring aba 1 2)
(substring aba 0 1)
(substring aba 1 2)))
(define (supports-ssl? str)
(define abas (append-map find-abas (unbracketed-parts str)))
(for*/or ([bab (in-list (map aba->bab abas))]
[str (in-list (bracketed-parts str))])
(regexp-match bab str)))