Day 15 solve part 1

1 files changed, 25 insertions, 0 deletions

diff --git a/AoC2022/15/solver.lisp b/AoC2022/15/solver.lisp
index 0166b23..584141f 100644
--- a/AoC2022/15/solver.lisp
+++ b/AoC2022/15/solver.lisp
@@ -80,3 +80,28 @@
             for l from (* (+ 10 ymin) stride)
             when (= 3 (aref grid l))
               count it))))
+
+(let* ((lines (uiop:read-file-lines "input"))
+       (markers (markers lines))
+       (bounds (bounds markers))
+       (max-distance (loop for (sensor beacon) on markers by #'cddr
+                           maximize (manhattan-dist sensor beacon))))
+
+  (destructuring-bind ((xmin xmax) (ymin ymax)) bounds
+    (let* ((stride (- (+ (* 2 max-distance) xmax 1) xmin))
+           (row-min (- xmin max-distance))
+           (target-row 2000000)
+           (row (make-array stride :element-type '(unsigned-byte 1) :initial-element 0)))
+      (loop for (sensor beacon) on markers by #'cddr
+            for distance = (manhattan-dist sensor beacon)
+            when (= target-row (cdr sensor))
+              do (setf (aref row (- (car sensor) row-min)) 1)
+            when (= target-row (cdr beacon))
+              do (setf (aref row (- (car beacon) row-min)) 1)
+
+            sum (loop
+                  for x from (- xmin distance) to (+ xmax distance)
+                  when (and (<= (manhattan-dist sensor (cons x target-row)) distance)
+                            (< -1 (- x row-min) stride)
+                            (= 0 (aref row (- x row-min))))
+                    count it and do (setf (aref row (- x row-min)) 1))))))