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;;; solver.el --- DAy 13 -*- lexical-binding: t; -*-
;;
;; Copyright (C) 2022 Óscar Nájera
;;
;; Author: Óscar Nájera <hi@oscarnajera.com>
;; Maintainer: Óscar Nájera <hi@oscarnajera.com>
;; Created: December 13, 2022
;; Modified: December 13, 2022
;;
;; This file is not part of GNU Emacs.
;;
;;; Commentary:
;;
;; DAy 13
;;
;;; Code:
(defun solver-input (filename &optional prepend)
(with-temp-buffer
(when prepend
(insert "[[2]]\n[[6]]\n"))
(insert-file-contents filename)
(goto-char (point-min))
(cl-loop
for a = (ignore-errors
(list
(json-parse-buffer :array-type 'list)
(json-parse-buffer :array-type 'list)))
while a
nconc a)))
(defun solver-compare (f s)
(cond
((eq f s) 'next)
((and (null f) (not (null s))) t)
((and (not (null f)) (null s)) nil)
((and (integerp f) (integerp s)) (< f s))
((and (integerp f) (consp s)) (solver-compare (list f) s))
((and (consp f) (integerp s)) (solver-compare f (list s)))
((let ((result (solver-compare (car f) (car s))))
(if (eq result 'next) (solver-compare (cdr f) (cdr s))
result)))))
(ert-deftest test-comparison ()
(should (eq (solver-compare 5 5) 'next))
(should (eq (solver-compare nil nil) 'next))
(should-not (solver-compare 5 nil))
(should (solver-compare nil 5))
(should (eq (solver-compare '(9) '((8 7))) nil))
(should (solver-compare '(1 1 3 1 1) '(1 1 5 1 1)))
(should (solver-compare '((1) (2 3 4)) '((1) 4)))
(should (solver-compare '() '(5))))
(defun solver-p1 (filename)
(cl-loop
for i from 1
for (a b) on (solver-input filename) by #'cddr
when (solver-compare a b)
sum i))
(ert-deftest test-1 ()
(should (= 13 (solver-p1 "eg-in")))
(should (= 5330 (solver-p1 "input"))))
(defun solver-p2 (filename)
(let ((sorted-packets (cl-sort (solver-input filename t) #'solver-compare)))
(cl-flet ((pick (item)
(1+ (cl-position
(cl-ecase item
('start '((2)))
('end '((6))))
sorted-packets :test #'equal))))
(* (pick 'start) (pick 'end)))))
(ert-deftest test-2 ()
(should (= 140 (solver-p2 "eg-in")))
(should (= 27648 (solver-p2 "input"))))
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