commit 61dc14d111cb4b73cde23efd139874acc1146f37
parent eba1e3d671fb248cdf9966ced55805a490815e97
Author: Lukas Henkel <lh@entf.net>
Date: Thu, 5 Dec 2024 07:06:24 +0100
Simplify
Diffstat:
1 file changed, 8 insertions(+), 22 deletions(-)
diff --git a/src/day-5.lisp b/src/day-5.lisp
@@ -12,17 +12,6 @@
#'parse-integer
(uiop:split-string line :separator '(#\,))))
-(defun update-ordered-p (update rules)
- (loop for (first second) in rules
- for pos-first = (position first update)
- for pos-second = (position second update)
- unless (or
- (null pos-first)
- (null pos-second)
- (< pos-first pos-second))
- do (return nil)
- finally (return t)))
-
(defun order-update (update rule-map)
(sort update (lambda (first second)
(not (gethash (list second first) rule-map)))))
@@ -31,8 +20,7 @@
(aref update (floor (length update) 2)))
(defun day-5 (input)
- (loop with rules = nil
- with rule-map = (make-hash-table :test #'equal)
+ (loop with rule-map = (make-hash-table :test #'equal)
with processing-updates = nil
with task-1 = 0
with task-2 = 0
@@ -40,15 +28,13 @@
until (null line)
do (cond
(processing-updates
- (let ((update (parse-update line)))
- (if (update-ordered-p update rules)
- (incf task-1 (middle-page-number update))
- (progn
- (setf update (order-update update rule-map))
- (incf task-2 (middle-page-number update))))))
+ (let* ((update (parse-update line))
+ (sorted (order-update (copy-seq update) rule-map))
+ (middle (middle-page-number sorted)))
+ (if (seq= update sorted)
+ (incf task-1 middle)
+ (incf task-2 middle))))
((string= line "")
(setf processing-updates t))
- (t (let ((rule (parse-rule line)))
- (setf (gethash rule rule-map) t)
- (push rule rules))))
+ (t (setf (gethash (parse-rule line) rule-map) t)))
finally (return (values task-1 task-2))))
