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;;; solver.el --- Day 08 -*- lexical-binding: t; -*-
;;
;; Copyright (C) 2022 Óscar Nájera
;;
;; Author: Óscar Nájera <hi@oscarnajera.com>
;; Maintainer: Óscar Nájera <hi@oscarnajera.com>
;; Created: December 09, 2022
;; Modified: December 09, 2022
;;
;; This file is not part of GNU Emacs.
;;
;;; Commentary:
;;
;; Day 08
;;
;;; Code:
(with-temp-buffer
(insert-file-contents "input")
(let* ((rows (split-string (buffer-string)))
(forest-depth (length rows))
(forest-width (length (car rows)))
(forest
(seq-mapcat
(lambda (row)
(cl-map 'vector (lambda (col) (logxor col 48)) row)) ;; 48 is the ascii 0
rows 'vector))
(visibility
(make-bool-vector (* forest-width forest-depth) nil))
(last-max -1))
(cl-flet ((update-visibility (index)
(let ((tree-height (aref forest index))
(mask-val (aref visibility index)))
(setf (aref visibility index) (or mask-val (< last-max tree-height)))
(setq last-max (max last-max tree-height)))))
;; left visible
(dotimes (i forest-width)
(setq last-max -1)
(dotimes (j forest-depth)
(update-visibility (+ j (* forest-width i)))))
;; top visible
(dotimes (j forest-depth)
(setq last-max -1)
(dotimes (i forest-width)
(update-visibility (+ j (* forest-width i)))))
;; rigth visible
(dotimes (i forest-width)
(setq last-max -1)
(cl-loop for j downfrom (1- forest-depth) to 0 do
(update-visibility (+ j (* forest-width i)))))
;; bottom visible
(dotimes (j forest-depth)
(setq last-max -1)
(cl-loop for i downfrom (1- forest-width) to 0 do
(update-visibility (+ j (* forest-width i))))))
(seq-partition
(cl-map 'vector #'identity
visibility) 5)
(cl-loop for v across visibility when v count it)
))
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