30 lines
929 B
Racket
30 lines
929 B
Racket
|
#lang racket
|
||
|
|
|
||
|
|
(require "../lib.rkt")
|
||
|
|
|
||
|
|
(define (parse line)
|
||
|
|
(match-let ([(list min max char pass)
|
||
|
|
(regexp-split #rx"[- ]" (regexp-replace #rx": " line " "))])
|
||
|
|
(list (string->number min)
|
||
|
|
(string->number max)
|
||
|
|
(string-ref char 0)
|
||
|
|
(string->list pass))))
|
||
|
|
|
||
|
|
(define input (map parse (problem-input 2)))
|
||
|
|
|
||
|
|
(define part1
|
||
|
|
(length (filter (λ (entry)
|
||
|
|
(match-let* ([(list min max char pass) entry]
|
||
|
|
[occurrences (length (filter (∂ char=? char) pass))])
|
||
|
|
(<= min occurrences max)))
|
||
|
|
input)))
|
||
|
|
|
||
|
|
(define part2
|
||
|
|
(length (filter (λ (entry)
|
||
|
|
(match-let* ([(list min max char pass) entry])
|
||
|
|
(xor (char=? (list-ref pass (sub1 min)) char)
|
||
|
|
(char=? (list-ref pass (sub1 max)) char))))
|
||
|
|
input)))
|
||
|
|
|
||
|
|
(show-solution part1 part2)
|