refactored and simplified

runs somewhat slower but no need for caching anymore.
much more minimalist

src/2024/day11.lisp

@@ -17,7 +17,6 @@
 (defun parse-line (line)
   (mapcar #'parse-integer (cl-ppcre:split " " line)))
 
-
 (defun parse-input (lines)
   (parse-line lines))
 
@@ -28,31 +27,20 @@
 (defparameter sample-data 
   (parse-input sample-text))
 
-
 (defun n-digits (x)
   (ceiling (log (1+ x) 10)))
 
 (defun evolve-stone (stone)
-  (let* ((n (n-digits stone))
-	 (split-factor (expt 10 (/ n 2))))
+  (let* ((n (n-digits stone)))
     (cond
       ((= 0 stone) (list 1))
-      ((evenp n) (list
-		  (floor (/ stone split-factor))
-		  (mod stone split-factor)))
+      ((evenp n) (let ((split-factor (expt 10 (/ n 2))))
+		   (list
+		    (floor (/ stone split-factor))
+		    (mod stone split-factor))))
       (t (list (* 2024 stone)))))
   )
 
-
-(defun merge-stone-map (map1 map2 &optional (multiplier 1))
-  (let ((result (copy-hash-table map1)))
-    (loop
-      for k being the hash-keys of map2
-      for v being the hash-values of map2
-      do (incf (gethash k result 0) (* v multiplier)))
-    result))
-
-
 (defun stones-to-stone-map (stones)
   (let ((result (make-hash-table :size (length stones))))
     (loop
@@ -63,22 +51,14 @@
 (defun total-stones (stone-map)
   (loop for v being the hash-values of stone-map sum v))
 
-(defparameter stone-map-cache (make-hash-table :size 1000))
-(defun map-stone (stone)
-  (let ((rslt (gethash stone stone-map-cache)))
-    (or rslt
-	(let ((stones (evolve-stone stone))
-	      (stone-map (make-hash-table)))
-	  (loop for s in stones
-		do (incf (gethash s stone-map 0)))
-	  (setf (gethash stone stone-map-cache) stone-map)))))
-
 (defun evolve-stone-map (stone-map)
   (let ((result (make-hash-table :size 1000)))
     (loop
       for k being the hash-keys of stone-map
       for v being the hash-values of stone-map
-      do (setf result (merge-stone-map result (map-stone k) v)))
+      do (loop
+	   for s in (evolve-stone k)
+	   do (incf (gethash s result 0) v)))
     result))
 
 (defun evolve-stone-map-n (stone-map n)
@@ -94,7 +74,6 @@
 (defun part2 (data)
   (format nil "~A" (total-stones (evolve-stone-map-n (stones-to-stone-map data) 75))))
 
-
 (defun solve-day ()
   (format t "part1: ~A~%" (part1 input-data))
   (format t "part2: ~A~%" (part2 input-data)))

tests/2024/day11-test.lisp

@@ -12,37 +12,12 @@
   (is equal '(125 17) (parse-line "125 17"))
   ) 
 
-
-
-(defparameter example-evolution
-  '((125 17)
-    (253000 1 7)
-    (253 0 2024 14168)
-    (512072 1 20 24 28676032)
-    (512 72 2024 2 0 2 4 2867 6032)
-    (1036288 7 2 20 24 4048 1 4048 8096 28 67 60 32)
-    (2097446912 14168 4048 2 0 2 4 40 48 2024 40 48 80 96 2 8 6 7 6 0 3 2)))
-
 (define-test test-evolve-stone
   :parent suite-2024-11
   (is equal '(1) (evolve-stone 0))
   (is equal '(9 9) (evolve-stone 99))
   (is equal '(2024) (evolve-stone 1)))
 
-(define-test test-evolve-stones
-  :parent suite-2024-11
-  (loop
-    for case in example-evolution
-    for expected in (subseq example-evolution 1)
-    do (is equal expected (evolve-stones case))    )
-  )
-
-
-
 (define-test+run test-part1
   :parent suite-2024-11
   (is equal "55312" (part1 sample-data)))
-
-(define-test+run test-part2
-                 :parent suite-2024-11
-                 (is equal nil (part2 sample-data)))