part2

1 files changed, 33 insertions, 4 deletions

diff --git a/AoC2023/day15/solver.lisp b/AoC2023/day15/solver.lisp
index fbcbf77..5bb2599 100644
--- a/AoC2023/day15/solver.lisp
+++ b/AoC2023/day15/solver.lisp
@@ -1,6 +1,6 @@
 ;; 17:04
 ;; 17:34 part1
-(ql:quickload '(fiveam str))
+(ql:quickload '(fiveam str arrows))
 
 (defparameter eg-in "rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7")
 
@@ -15,9 +15,38 @@
           (str:split "," (str:trim in))
           :key #'hash))
 
+(defun implement-instructions (instructions &aux (boxes (make-array 256 :initial-element nil)))
+  (cl-ppcre:do-register-groups (label operator (#'parse-integer focal-length))
+      ("(\\w+)([=-])(\\d+)?" instructions)
+    (let ((content
+            (aref boxes (hash label))))
+      (flet ((is-lens (c) (equal (car c) label)))
+        (arrows:->>
+         (cond
+           ((equal "-" operator)
+            (remove-if #'is-lens content))
+           ((equal "=" operator)
+            (if (zerop (count-if #'is-lens content))
+                (append content (list (cons label focal-length)))
+                (mapcar
+                 (lambda (c) (if (is-lens c)
+                                 (cons label focal-length)
+                                 c))
+                 content))))
+         (setf (aref boxes (hash label)))))))
+  boxes)
+
+(defun focusing-power (boxes)
+  (loop for i from 1
+        for lenses across boxes
+        sum
+        (* i (loop for j from 1
+                   for (l . fl) in lenses
+                   sum (* j fl)))))
+
 (fiveam:test solutions
   (fiveam:is (= 52 (hash "HASH")))
   (fiveam:is (= 1320 (solve1 eg-in)))
-  (fiveam:is (= 506437 (solve1 (uiop:read-file-string "input")))))
-
-(fiveam:run!)
+  (fiveam:is (= 506437 (solve1 (uiop:read-file-string "input"))))
+  (fiveam:is (= 145 (focusing-power (implement-instructions eg-in))))
+  (fiveam:is (= 288521 (focusing-power (implement-instructions (uiop:read-file-string "input"))))))