commit c3dffd28b9750ff8439ddddc5b5fece451000406 parent 8c78fb5cb90087550a894bd7d8d992922ece70ce Author: Lukas Henkel <lh@entf.net> Date: Wed, 20 Dec 2023 21:30:38 +0100 Day 20 task 2 Diffstat:
| M | src/day-20.lisp | | | 42 | ++++++++++++++++++++++++++++-------------- |
1 file changed, 28 insertions(+), 14 deletions(-)
diff --git a/src/day-20.lisp b/src/day-20.lisp @@ -95,17 +95,31 @@ modules)) (defun day-20 (input) - (let* ((modules (parse-input input)) - (broadcast (gethash "broadcaster" modules))) - (loop with low-count = 0 - with high-count = 0 - repeat 1000 - do (loop with next = (list (list nil broadcast :low)) - while next - for next-next = (loop for (from to type) in next - do (ecase type - (:low (incf low-count)) - (:high (incf high-count))) - nconc (pulse to from type)) - do (setf next next-next)) - finally (return (* low-count high-count))))) + (loop with modules = (parse-input input) + with broadcast = (gethash "broadcaster" modules) + with rx-source-modules = (when-let (rx (gethash "rx" modules)) + (module-connected (first (module-connected rx)))) + with rx-source-intervals = (make-hash-table) + with task-1 = 0 + with task-2 = 0 + with low-count = 0 + with high-count = 0 + for i from 1 + do (loop with next = (list (list nil broadcast :low)) + while next + for n = (loop for (from to type) in next + do (ecase type + (:low (incf low-count)) + (:high (progn + (when (and (member from rx-source-modules) + (not (gethash from rx-source-intervals))) + (setf (gethash from rx-source-intervals) i)) + (incf high-count)))) + nconc (pulse to from type)) + do (setf next n)) + when (= i 1000) + do (setf task-1 (* low-count high-count)) + when (= (hash-table-count rx-source-intervals) (length rx-source-modules)) + do (setf task-2 (apply #'lcm (hash-table-values rx-source-intervals))) + when (if rx-source-modules (> task-2 0) (> task-1 0)) + do (return (values task-1 task-2))))