From f34c85b78a1cbefa475a252184c13b68c9727332 Mon Sep 17 00:00:00 2001
From: Oscar Najera <hi@oscarnajera.com>
Date: Tue, 6 Dec 2022 16:47:44 +0100
Subject: [AoC2022] Lisp 06

---
 AoC2022/06/solver.lisp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 AoC2022/06/solver.lisp

(limited to 'AoC2022/06/solver.lisp')

diff --git a/AoC2022/06/solver.lisp b/AoC2022/06/solver.lisp
new file mode 100644
index 0000000..36aab05
--- /dev/null
+++ b/AoC2022/06/solver.lisp
@@ -0,0 +1,17 @@
+
+(defun solver (marker-size)
+  (with-open-file (in "input" :element-type 'unsigned-byte)
+    (loop with acc = (make-array marker-size :element-type 'unsigned-byte)
+          for char = (ash 1 (- (read-byte in) 96)) ;; all lowercase letters thus subtract ascii start
+          and idx from 1
+          do (setf (aref acc (mod idx marker-size)) char)
+          when (<= marker-size (logcount (reduce (lambda (set v) (logxor set v)) acc)))
+            return idx)))
+
+(ql:quickload :fiveam)
+
+(fiveam:test results
+             (fiveam:is (= 1655 (solver 4)))
+             (fiveam:is (= 2665 (solver 14))))
+
+(fiveam:run-all-tests)
-- 
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