1 files changed, 110 insertions, 0 deletions
diff --git a/users/tazjin/aoc2023/day3.el b/users/tazjin/aoc2023/day3.el
new file mode 100644
index 000000000000..dd39c1b836d3
--- /dev/null
+++ b/users/tazjin/aoc2023/day3.el
@@ -0,0 +1,110 @@
+(defun aoc23d3-symbol-p (c)
+  (not (or (= c ? )
+           (and (>= c ?0)
+                (<= c ?9)))))
+
+(defun rectangle-for-bounds (bounds)
+  (let* ((start (save-excursion
+                     (goto-char (car bounds))
+                     (let ((col (current-column)))
+                       (forward-line -1)
+                       (move-to-column (max 0 (1- col))))
+                     (point)))
+         (end (save-excursion
+                (goto-char (cdr bounds))
+                (let ((col (current-column)))
+                  (forward-line 1)
+                  (move-to-column (1+ col)))
+                (point))))
+    (list start end)))
+
+(defun get-machine-part ()
+  (interactive)
+  (when-let* ((num-raw (number-at-point))
+              (num (abs num-raw))
+              ;; handles negative number edge case (bounds contain the `-')
+              (bounds-raw (bounds-of-thing-at-point 'number))
+              (bounds (if (< num-raw 0)
+                          (cons (1- (car bounds-raw)) (cdr bounds-raw))
+                        bounds-raw))
+              (rectangle (rectangle-for-bounds bounds))
+              (neighbours (apply #'concat
+                                 (apply #'extract-rectangle rectangle))))
+    (if (-any #'aoc23d3-symbol-p (string-to-list neighbours))
+        (cons num rectangle)
+      (cons nil rectangle))))
+
+
+(defun find-machine-parts (input)
+  (with-temp-buffer
+    (insert input)
+    (goto-char (point-min))
+    (save-excursion
+      (replace-string "." " "))
+
+    (cl-loop while (forward-word)
+             for result = (get-machine-part)
+             when (car result) collect (car result))))
+
+
+;; debugging
+
+(defvar aoc23d3-example "467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..")
+
+(defvar aoc23d3-example2 "12.......*..
++.........34
+.......-12..
+..78........
+..*....60...
+78..........
+.......23...
+....90*12...
+............
+2.2......12.
+.*.........*
+1.1.......56")
+
+(defvar aoc23d3-example3 "243.
+..*.
+....")
+
+(defun aoc23d3-debug (p)
+  "Interactive debugger for the solution, can be bound to a key in
+an input buffer. Dots should already have been replaced with
+spaces."
+  (interactive "P")
+  (unless p
+    (goto-char aoc23d3-last))
+  (rectangle-mark-mode 1)
+  (forward-word)
+  (setq aoc23d3-last (point))
+  (pcase (get-machine-part)
+    (`(nil ,b ,e) (progn (set-mark b)
+                          (goto-char e)
+                          (set-face-attribute 'region nil :background "#FAA0A0")))
+    (`(,num ,b ,e) (progn (set-mark b)
+                          (goto-char e)
+                          (set-face-attribute 'region nil :background "#d1ffbd")))
+    (other (deactivate-mark))))
+
+(cl-assert (= 4361 (-sum (find-machine-parts aoc23d3-example))) nil
+           "example from website is working")
+
+(cl-assert (= 413 (-sum (find-machine-parts aoc23d3-example2))) nil
+           "example from subreddit is working")
+
+(cl-assert (= 243 (-sum (find-machine-parts aoc23d3-example3))) nil
+           "example from telegram is working")
+
+;; day 1 (incomplete)
+
+(-sum (find-machine-parts (s-trim (f-read "~/Downloads/input.txt"))))