Refactor

1 files changed, 18 insertions, 24 deletions

diff --git a/2024/11/puzzles.lisp b/2024/11/puzzles.lisp
index 9c3c73b..7d44a0b 100644
--- a/2024/11/puzzles.lisp
+++ b/2024/11/puzzles.lisp
@@ -3,9 +3,8 @@
 (defparameter *memo* (make-hash-table :test 'equal))
 
 (defun main (filename blink-count)
-  (let ((stones (read-stones filename)))
-    (loop for stone in stones
-          sum (count-stones stone blink-count))))
+  (loop for stone in (read-stones filename)
+        sum (count-stones stone blink-count)))
 
 (defun read-stones (filename)
   (with-open-file (stream filename)
@@ -14,33 +13,28 @@
       (read-from-string (concatenate 'string "(" contents ")")))))
 
 (defun count-stones (stone blink-count)
-  (or (gethash (cons stone blink-count) *memo*)
-      (setf (gethash (cons stone blink-count) *memo*)
-            (cond ((= (decf blink-count) -1)
-                   1)
-                  ((= stone 0)
-                   (count-stones 1 blink-count))
-                  ((evenp (integer-digit-count stone))
-                   (let ((hi-lo (integer-split stone)))
-                     (+ (count-stones (car hi-lo) blink-count)
-                        (count-stones (cdr hi-lo) blink-count))))
-                  (:else
-                   (count-stones (* 2024 stone) blink-count))))))
+  (let ((stone+blink-count (cons stone blink-count)))
+    (or (gethash stone+blink-count *memo*)
+        (setf (gethash stone+blink-count *memo*)
+              (cond ((minusp (decf blink-count))
+                     1)
+                    ((zerop stone)
+                     (count-stones 1 blink-count))
+                    ((evenp (integer-digit-count stone))
+                     (multiple-value-bind (hi lo) (integer-split stone)
+                       (+ (count-stones hi blink-count)
+                          (count-stones lo blink-count))))
+                    (:else
+                      (count-stones (* 2024 stone) blink-count)))))))
 
 (defun integer-digit-count (x)
-  (loop with n = 0
-        while (/= x 0)
-        do (progn (incf n) (setq x (floor x 10)))
-        finally (return n)))
+  (1+ (truncate (log x 10))))
 
 (defun integer-split (x)
-  (let* ((n (floor (integer-digit-count x) 2))
-         (m (expt 10 n)))
-    (cons (floor x m)
-          (mod x m))))
+  (floor x (expt 10 (floor (integer-digit-count x) 2))))
 
 ;; START PART 1
 (format t "~d~%" (main "input" 25))
 ;; END PART 1 START PART 2
 (format t "~d~%" (main "input" 75))
-;; END PART 2
\ No newline at end of file
+;; END PART 2