aoc-2022/scheme/day-6/solution.scm
2022-12-14 03:02:12 -05:00

46 lines
1.7 KiB
Scheme
Executable file

#!/usr/bin/env -S guile -s
!#
;; Copyright (C) 2022
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <https://www.gnu.org/licenses/>.
(use-modules (srfi srfi-1)
(ice-9 match)
(advent-of-code))
(define (all-different? list)
(match list
(() '())
((_) #t)
((head . tail) (if (member head tail)
#f
(all-different? tail)))))
(define (solution input marker-length)
(let loop ((position 0))
(let ((marker (take (drop input position) marker-length)))
(if (all-different? marker)
(+ position marker-length)
(loop (+ position 1))))))
(should-equal (all-different? '(a b c d)) #t)
(should-equal (all-different? '(a a b c)) #f)
(should-equal 7 (solution (string->list "mjqjpqmgbljsphdztnvjfqwrcgsmlb") 4))
(should-equal 5 (solution (string->list "bvwbjplbgvbhsrlpgdmjqwftvncz") 4))
(should-equal 6 (solution (string->list "nppdvjthqldpwncqszvftbrmjlhg") 4))
(should-equal 10 (solution (string->list "nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg") 4))
(should-equal 11 (solution (string->list "zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw") 4))
(should-equal 1794 (solution (string->list (read-file "input.txt")) 4))