135 lines
5 KiB
Common Lisp
135 lines
5 KiB
Common Lisp
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#!/usr/bin/env -S sbcl --script
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;; Copyright (C) 2022
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;; This program is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; This program is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with this program. If not, see <https://www.gnu.org/licenses/>.
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(require 'asdf)
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(require 'uiop)
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(require 'str)
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(require 'iterate)
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(defpackage :advent-of-code-day-8
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(:use :cl :iterate))
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(in-package :advent-of-code-day-8)
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(defclass tree ()
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((x
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:initarg :x
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:reader x)
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(y
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:initarg :y
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:reader y)))
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(defmacro make-tree (x y)
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`(make-instance 'tree :x ,x :y ,y))
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(defun scan-right? (trees position)
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(iter (with width = (- (array-dimension trees 1) 1))
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(with tree-height = (aref trees (y position) (x position)))
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(for i from (+ (x position) 1) to width)
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(for tree = (aref trees (y position) i))
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(counting t into view-count)
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(unless (< tree tree-height)
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(return (cons :not-visible view-count)))
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(finally (return (cons :visible view-count)))))
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(defun scan-left? (trees position)
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(iter (with tree-height = (aref trees (y position) (x position)))
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(for i from (- (x position) 1) downto 0)
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(for tree = (aref trees (y position) i))
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(counting t into view-count)
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(unless (< tree tree-height)
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(return (cons :not-visible view-count)))
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(finally (return (cons :visible view-count)))))
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(defun scan-down? (trees position)
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(iter (with height = (- (array-dimension trees 0) 1))
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(with tree-height = (aref trees (y position) (x position)))
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(for i from (+ (y position) 1) to height)
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(for tree = (aref trees i (x position)))
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(counting t into view-count)
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(unless (< tree tree-height)
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(return (cons :not-visible view-count)))
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(finally (return (cons :visible view-count)))))
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(defun scan-up? (trees position)
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(iter (with tree-height = (aref trees (y position) (x position)))
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(for i from (- (y position) 1) downto 0)
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(for tree = (aref trees i (x position)))
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(counting t into view-count)
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(unless (< tree tree-height)
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(return (cons :not-visible view-count)))
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(finally (return (cons :visible view-count)))))
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(defun tree-visible? (trees position)
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(or (equal (car (scan-right? trees position)) :visible)
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(equal (car (scan-left? trees position)) :visible)
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(equal (car (scan-down? trees position)) :visible)
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(equal (car (scan-up? trees position)) :visible)))
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(defun scenic-score (trees tree)
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(* (cdr (scan-right? trees tree))
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(cdr (scan-left? trees tree))
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(cdr (scan-down? trees tree))
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(cdr (scan-up? trees tree))))
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(defun trees-from-file-lines (lines)
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(let* ((split-lines-into-digits (mapcar (lambda (line)
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(str:split "" line :omit-nulls t))
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lines))
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(numbers (mapcar (lambda (row)
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(mapcar 'parse-integer row))
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split-lines-into-digits))
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(x (length (nth 0 numbers)))
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(y (length numbers)))
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(make-array (list x y) :initial-contents numbers)))
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(defun solution-part-1 (trees)
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(iter (with width = (- (array-dimension trees 1) 1))
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(with height = (- (array-dimension trees 0) 1))
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(for y from 1 to (- height 1))
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(sum (iter (for x from 1 to (- width 1))
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(for tree = (make-instance 'tree :x x :y y))
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(counting (tree-visible? trees tree)))
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into visible-interior-trees)
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(finally (return (+ visible-interior-trees (* width 2) (* height 2))))))
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(defun solution-part-2 (trees)
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(iter (with width = (- (array-dimension trees 1) 1))
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(with height = (- (array-dimension trees 0) 1))
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(for y from 1 to (- height 1))
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(appending (iter (for x from 1 to (- width 1))
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(for tree = (make-instance 'tree :x x :y y))
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(collect (scenic-score trees tree)))
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into scores)
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(finally (return (let* ((sorted-scores (sort scores '>)))
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(car sorted-scores))))))
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(let ((trees (trees-from-file-lines (uiop:read-file-lines "example.txt"))))
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(assert (= 21 (solution-part-1 trees))))
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(let ((trees (trees-from-file-lines (uiop:read-file-lines "input.txt"))))
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(assert (= 1736 (solution-part-1 trees))))
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(let ((trees (trees-from-file-lines (uiop:read-file-lines "example.txt"))))
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(assert (= 8 (solution-part-2 trees))))
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(let ((trees (trees-from-file-lines (uiop:read-file-lines "input.txt"))))
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(assert (= 268800 (solution-part-2 trees))))
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;; Local Variables:
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;; mode: lisp
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;; End:
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