advent-of-code-2023

commit be76554e85d7a77b4e6a473b9761762daa0ee338
parent b422a1c50fd4de5f2f29dee2e1ad6d62fc2d4915
Author: Lukas Henkel <lh@entf.net>
Date:   Wed, 13 Dec 2023 06:42:18 +0100

Day 13 task 1

Diffstat:
A
input/13.txt
 | 
1311
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
src/day-13.lisp
 | 
38
++++++++++++++++++++++++++++++++++++++
M
src/utils.lisp
 | 
14
++++++++++----
A
t/day-13.lisp
 | 
23
+++++++++++++++++++++++

4 files changed, 1382 insertions(+), 4 deletions(-)
diff --git a/input/13.txt b/input/13.txt
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diff --git a/src/day-13.lisp b/src/day-13.lisp
@@ -0,0 +1,38 @@
+(defpackage #:aoc/day-13
+  (:use #:cl #:aoc/utils)
+  (:export #:day-13))
+(in-package #:aoc/day-13)
+
+(defun find-vertical-point-of-reflection (map)
+  (loop with width = (input-map-width map)
+        with height = (input-map-height map)
+        for reflection-x from 0 below (1- width)
+        for reflection-length = (min (1+ reflection-x)
+                                     (- width reflection-x 1))
+        when (loop repeat reflection-length
+                   for x-1 downfrom reflection-x
+                   for x-2 from (1+ reflection-x)
+                   always (loop for y from 0 below height
+                                always (char= (map-cell map (cons x-1 y))
+                                              (map-cell map (cons x-2 y)))))
+          do (return (1+ reflection-x))))
+
+(defun find-horizontal-point-of-reflection (map)
+  (loop with width = (input-map-width map)
+        with height = (input-map-height map)
+        for reflection-y from 0 below (1- height)
+        for reflection-length = (min (1+ reflection-y)
+                                     (- height reflection-y 1))
+        when (loop repeat reflection-length
+                   for y-1 downfrom reflection-y
+                   for y-2 from (1+ reflection-y)
+                   always (loop for x from 0 below width
+                                always (char= (map-cell map (cons x y-1))
+                                              (map-cell map (cons x y-2)))))
+          do (return (1+ reflection-y))))
+
+(defun day-13 (input)
+  (loop for map = (make-map input)
+        while map
+        sum (or (find-vertical-point-of-reflection map)
+                (* (find-horizontal-point-of-reflection map) 100))))
diff --git a/src/utils.lisp b/src/utils.lisp
@@ -7,6 +7,7 @@
    #:read-input-match
    #:char-number
    #:make-map
+   #:print-map
    #:input-map
    #:input-map-width
    #:input-map-height
@@ -94,13 +95,18 @@
         with data = nil
         for row = (read-line input nil)
         for height from 0
-        while row
+        while (and row (> (length row) 0))
         when (= height 0)
           do (setf width (length row))
         do (push row data)
-        finally (return (make-input-map :data (coerce (nreverse data) 'vector)
-                                        :width width
-                                        :height height))))
+        finally (return (and data
+                             (make-input-map :data (coerce (nreverse data) 'vector)
+                                             :width width
+                                             :height height)))))
+
+(defun print-map (map &key (stream *standard-output*))
+  (loop for y from 0 below (input-map-height map)
+        do (format stream "~A~%" (aref (input-map-data map) y))))
 
 (declaim (inline point+ point- point-x point-y)
          (ftype (function (cons) fixnum) point-x point-y))
diff --git a/t/day-13.lisp b/t/day-13.lisp
@@ -0,0 +1,23 @@
+(defpackage #:aoc-test/day-13
+  (:use #:cl #:lisp-unit2))
+(in-package #:aoc-test/day-13)
+
+(define-test test-day-13
+    ()
+  (multiple-value-bind (task-1 task-2)
+      (aoc:run-day 13 "#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#")
+    (assert= 405 task-1)))