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;;; solver.el --- Day 05 -*- lexical-binding: t; -*-
;;
;; Copyright (C) 2022 Óscar Nájera
;;
;; Author: Óscar Nájera <hi@oscarnajera.com>
;; Maintainer: Óscar Nájera <hi@oscarnajera.com>
;; Created: December 05, 2022
;; Modified: December 05, 2022
;;
;; This file is not part of GNU Emacs.
;;
;;; Commentary:
;;
;; Day 05
;;
;;; Code:
(require 'subr-x)
(defun solver-build-stacks ()
(let* ((stacks-len (length
(split-string
(buffer-substring-no-properties (line-beginning-position) (line-end-position)))))
(stacks (make-vector stacks-len nil))
next)
(while (setq next (search-backward "]" nil t))
(push (char-before)
(aref stacks (/ (- next (line-beginning-position) 1) 4))))
stacks))
(defun solver-single-move! (stacks amount from to)
(dotimes (_ amount)
(push (pop (aref stacks from)) (aref stacks to))))
(defun solver-bulk-move! (stacks amount from to)
(setf (aref stacks to)
(append (seq-take (aref stacks from) amount)
(aref stacks to)))
(setf (aref stacks from) (seq-drop (aref stacks from) amount)))
(defun solver-apply-moves (execution stacks)
(while (re-search-forward (rx bol "move " (group (+ digit)) " from " (group (+ digit)) " to " (group (+ digit))) nil t)
(let ((amount (string-to-number (match-string 1)))
(from (1- (string-to-number (match-string 2))))
(to (1- (string-to-number (match-string 3)))))
(funcall execution stacks amount from to)))
stacks)
(defun solver (execution)
(with-temp-buffer
(insert-file-contents "input")
(re-search-forward "^ 1")
(thread-last
(solver-build-stacks)
(solver-apply-moves execution)
(cl-map 'string #'car))))
(ert-deftest solver-solutions ()
(should (equal "TPGVQPFDH"
(solver #'solver-single-move!)))
(should (equal "DMRDFRHHH"
(solver #'solver-bulk-move!))))
(provide 'solver)
;;; solver.el ends here
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