aoc-2022/elisp/day-4/solution.el

#!/usr/bin/env -S emacs --script

;; -*- lexical-binding: t; -*-

;; 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/>.

(add-to-list 'load-path default-directory)

(require 'ert)
(require 'advent-of-code)

(defun solution-parse-pair (s)
  (let ((parts (string-split s "-")))
    (cons (string-to-number (car parts))
          (string-to-number (cadr parts)))))

(defun solution-parse-pairs (line)
  (let ((unparsed-pairs (string-split line "," t)))
    (list (solution-parse-pair (car unparsed-pairs))
          (solution-parse-pair (cadr unparsed-pairs)))))

(defun solution-pair-contains? (a b)
  (and (<= (car a) (car b))
       (>= (cdr a) (cdr b))))

(defun solution-pair-overlaps? (a b)
  (or (and (>= (car a) (car b))
           (<= (car a) (cdr b)))
      (and (>= (cdr a) (car b))
           (<= (cdr a) (cdr b)))))

(defun solution-part-1 (input)
  (let ((pairs (seq-map 'solution-parse-pairs input)))
    (seq-count (lambda (pair)
                   (or (solution-pair-contains? (car pair) (cadr pair))
                       (solution-pair-contains? (cadr pair) (car pair))))
               pairs)))

(defun solution-part-2 (input)
  (let ((pairs (seq-map 'solution-parse-pairs input)))
    (seq-count (lambda (pair)
                 (or (solution-pair-overlaps? (car pair) (cadr pair))
                     (solution-pair-overlaps? (cadr pair) (car pair))))
               pairs)))

(ert-deftest solution-part-1-example ()
  (should (equal (solution-part-1 (aoc-read-file-lines "example.txt")) 2)))

(ert-deftest solution-part-1 ()
  (should (equal (solution-part-1 (aoc-read-file-lines "input.txt")) 644)))

(ert-deftest solution-part-2-example ()
  (should (equal (solution-part-2 (aoc-read-file-lines "example.txt")) 4)))

(ert-deftest solution-part-2 ()
  (should (equal (solution-part-2 (aoc-read-file-lines "input.txt")) 926)))

(when noninteractive
  (ert-run-tests-batch))

;; Local Variables:
;; read-symbol-shorthands: (("solution-" . "advent-of-code-day-4-") ("aoc-" . "advent-of-code-"))
;; End: