day 18, part 1, the simple one

day18.lisp

@@ -0,0 +1,48 @@
+;; https://adventofcode.com/2022/day/18
+
+(ql:quickload 'cl-ppcre)
+
+(defun coords-from-input (file-name)
+  (mapcar
+   (lambda (line)
+     (mapcar #'parse-integer (cl-ppcre:split "," line)))
+   (uiop:read-file-lines file-name)))
+
+(defun find-maxes (all-coords)
+ (loop
+  for (x y z) in all-coords
+  maximize (1+ x) into xs
+  maximize (1+ y) into ys
+  maximize (1+ z) into zs
+  finally (return (list xs ys zs))) )
+
+(defun fill-connectivity-array (all-coords connectivity-matrix)
+  (loop
+    for (x y z) in all-coords
+    do (setf (aref connectivity-matrix x y z) 1)))
+
+(defun neighbors-for (coords connectivity-matrix)
+  (labels ((coords-fit (potential-point)
+             (loop for i from 0 to 2
+                   always (and (< (nth i potential-point)
+                                  (array-dimension connectivity-matrix i))
+                               (>= (nth i potential-point) 0)))))
+    (loop
+      for deltas in  `((1 0 0) (-1 0 0)
+                       (0 1 0) (0 -1 0)
+                       (0 0 1) (0 0 -1))
+      for neighbor = (mapcar #'+ coords deltas)
+      when
+      (and (coords-fit neighbor)
+           (= 1 (apply #'aref connectivity-matrix neighbor)))
+      collect neighbor)))
+
+(defun count-open-sides (connectivity-matrix)
+  (destructuring-bind (n m k)
+      (array-dimensions connectivity-matrix)
+    (loop for x from 0 below n sum
+          (loop for y from 0 below m sum
+                (loop for z from 0 below k
+                      when (= 1 (aref connectivity-matrix x y z))
+                      summing (- 6
+                      (length (neighbors-for (list x y z) connectivity-matrix))))))))