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