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;;; solver.el --- Day 03 -*- lexical-binding: t; -*-
;;
;; Copyright (C) 2022 Óscar Nájera
;;
;; Author: Óscar Nájera <hi@oscarnajera.com>
;; Maintainer: Óscar Nájera <hi@oscarnajera.com>
;; Created: December 04, 2022
;; Modified: December 04, 2022
;;
;; This file is not part of GNU Emacs.
;;
;;; Commentary:
;;
;; Day 03
;;
;;; Code:
(require 'subr-x)
(defsubst solver-recover-value (cross)
(let ((result 0))
(while (= 0 (logand cross 1))
(setq cross (ash cross -1))
(cl-incf result))
result))
(ert-deftest test-recover ()
(should (eq ?t (+ 64 (solver-recover-value (ash 1 (- ?t 64))))))
(should (eq ?s (+ 64 (solver-recover-value (ash 1 (- ?s 64))))))
(should (eq ?C (+ 64 (solver-recover-value (ash 1 (- ?C 64))))))) ;; small cap starts at a=97, but already took 64
(defsubst solver-to-priority (value)
(if (< value 31) ;; It is a capital letter in range [1;26]
(+ value 26)
(- value 32)))
(defun solver-line-priority (str)
(cl-assert (length> str 0))
(let ((mid (/ (length str) 2))
(left-pack 0) (right-pack 0))
(cl-loop for l across (substring str 0 mid)
for r across (substring str mid)
do (progn
(setf left-pack (logior left-pack (ash 1 (- l 64)))) ;; ASCII letters start at 65=A
(setf right-pack (logior right-pack(ash 1 (- r 64)))))
for cross = (logand left-pack right-pack)
when (< 0 cross)
return (solver-to-priority (solver-recover-value cross)))))
(ert-deftest test-line-priority ()
(should (= 16 (solver-line-priority "vJrwpWtwJgWrhcsFMMfFFhFp")))
(should (= 19 (solver-line-priority "hMHLcmGLMLhHmsRMsSvsQSqrsrlJTTdV" )))
(should (= 20 (solver-line-priority "ttgJtRGJQctTZtZT"))))
(defsubst solver-badge (packs)
(seq-reduce (lambda (acc item)
(logior acc (ash 1 (- item 64))))
packs 0))
(defun solver-badge-priority (group-packs)
(thread-last group-packs
(split-string)
(mapcar #'solver-badge)
(apply #'logand)
(solver-recover-value)
(solver-to-priority)))
(defun solver (task lines)
(with-temp-buffer
(insert-file-contents "input")
(goto-char (point-min))
(cl-loop while (not (eobp))
sum
(funcall task
(buffer-substring-no-properties (point)
(line-end-position lines)))
do (forward-line lines))))
(ert-deftest test-problems ()
(should (= 8072 (solver #'solver-line-priority 1)))
(should (= 2567 (solver #'solver-badge-priority 3))))
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