[AoC2023] day14 part1

1 files changed, 35 insertions, 0 deletions

diff --git a/AoC2023/day14/solve.lisp b/AoC2023/day14/solve.lisp
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+++ b/AoC2023/day14/solve.lisp
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+;; 9:39 start
+;; 10:17 part 1
+;;
+(ql:quickload '(fiveam))
+
+(defun roll-rocks (field)
+  (loop for row from 1 below (array-dimension field 0)
+        sum
+        (loop for col below (array-dimension field 1)
+              when (and (eq #\O (aref field row col))
+                        (eq #\. (aref field (1- row) col)))
+                do (setf (aref field (1- row) col) #\O
+                         (aref field row col) #\.)
+                and count t)))
+
+(defun array-slice (arr row)
+  (make-array (array-dimension arr 1)
+              :displaced-to arr
+              :displaced-index-offset (* row (array-dimension arr 1))))
+
+(defun solve (input)
+  (let* ((rows (length input))
+         (field
+           (make-array (list rows (length (car input))) :initial-contents input)))
+    (loop
+      for result = (roll-rocks field)
+      until (zerop result))
+    (loop for row below rows
+          sum (* (- rows row) (count #\O (array-slice field row))))))
+
+(fiveam:test solutions
+  (fiveam:is (= 136 (solve (uiop:read-file-lines "eg-in"))))
+  (fiveam:is (= 108935 (solve (uiop:read-file-lines "input")))))
+
+(fiveam:run!)