1 files changed, 85 insertions, 0 deletions
diff --git a/AoC2023/day13/solver.lisp b/AoC2023/day13/solver.lisp
new file mode 100644
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+++ b/AoC2023/day13/solver.lisp
@@ -0,0 +1,85 @@
+(ql:quickload '(fiveam))
+
+(defparameter eg-vert "#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#")
+
+(defparameter eg-horizontal "#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.")
+
+(defun find-repeat (rows)
+  (loop for (one two-or-nil) on rows by #'cdr
+        for idx from 0
+        when (and (not (null two-or-nil))
+                  (equal one two-or-nil))
+          collect (1+ idx)))
+
+(defun find-v-mirror (rows)
+  (remove-if-not (lambda (n) (v-mirror-p rows n))
+                 (find-repeat rows)))
+
+(defun v-mirror-p (rows idx)
+  (every #'equal
+         (reverse (subseq rows 0 idx))
+         (subseq rows idx)))
+
+
+(defun find-h-mirror (rows)
+  (find-v-mirror
+   (transpose-rows rows)))
+
+(defun transpose-rows (rows)
+  (arrows:-<>
+   rows
+   (mapcar #'string-to-octets <>)
+   (apply #'map 'list (lambda (&rest vals)
+                        (coerce (mapcar #'code-char vals) 'string)) <>)))
+
+(fiveam:test partials
+  (fiveam:is
+   (equal '(4)
+          (find-repeat
+           (cl-ppcre:split "\\n" eg-vert))))(fiveam:is
+   (equal '(4)
+          (find-v-mirror
+           (cl-ppcre:split "\\n" eg-vert))))
+
+  (fiveam:is
+   (equal '(3)
+          (find-repeat
+           (cl-ppcre:split "\\n" eg-horizontal))))
+  (fiveam:is
+   (null (find-v-mirror
+          (cl-ppcre:split "\\n" eg-horizontal))))
+  (fiveam:is
+   (equal '(5)
+          (find-h-mirror
+           (cl-ppcre:split "\\n" eg-horizontal)))))
+
+(defun solver (maps)
+  (let ((verical-mirrors (delete nil (mapcan #'find-v-mirror maps)))
+        (horizontal-mirrors (delete nil (mapcan #'find-h-mirror maps))))
+    (+
+     (* 100 (apply #'+ verical-mirrors))
+     (apply #'+ horizontal-mirrors))))
+
+(defun parse-input (file)
+  (arrows:->>
+   (uiop:read-file-string file)
+   (cl-ppcre:split "\\n\\n")
+   (mapcar (lambda (map) (cl-ppcre:split "\\n" map)))))
+
+(fiveam:test solutions
+  (fiveam:is (= 405 (solver (parse-input "eg-in"))))
+  (fiveam:is (= 35360 (solver (parse-input "input")))))
+
+(fiveam:run!)