day 8 CL

2 files changed, 55 insertions, 0 deletions

diff --git a/AoC2022/08/eg-in b/AoC2022/08/eg-in
new file mode 100644
index 0000000..16d6fbd
--- /dev/null
+++ b/AoC2022/08/eg-in
@@ -0,0 +1,5 @@
+30373
+25512
+65332
+33549
+35390
diff --git a/AoC2022/08/solver.lisp b/AoC2022/08/solver.lisp
new file mode 100644
index 0000000..e3b63e5
--- /dev/null
+++ b/AoC2022/08/solver.lisp
@@ -0,0 +1,50 @@
+(ql:quickload '(fiveam uiop))
+
+(defun coord (width height)
+  (lambda (x y)
+    (when (and (< -1 x width)
+               (< -1 y height))
+      (+ x (* y width)))))
+
+(let* ((data (uiop:read-file-lines "input"))
+       (width (length (car data)))
+       (height (length data))
+       (forest-arr
+         (apply #'vector
+                (mapcan (lambda (row)
+                          (map 'list (lambda (x) (- (char-code x) 48)) row)) data)))
+       (visibility-mask (make-array (* width height) :initial-element nil))
+       (location (coord width height)))
+  (dotimes (y height)
+    ;; left watch
+    (loop
+      for x from 0 below width
+      for maxh = -1 then (max maxh tree-height)
+      for tree-height = (aref forest-arr (funcall location x y))
+      when (> tree-height maxh)
+        do (setf (aref visibility-mask (funcall location x y)) t))
+    ;; right watch
+    (loop
+      for x downfrom (1- width) to 0
+      for maxh = -1 then (max maxh tree-height)
+      for tree-height = (aref forest-arr (funcall location x y))
+      when (> tree-height maxh)
+        do (setf (aref visibility-mask (funcall location x y)) t)))
+
+  (dotimes (x width)
+    ;; top watch
+    (loop
+      for y from 0 below height
+      for maxh = -1 then (max maxh tree-height)
+      for tree-height = (aref forest-arr (funcall location x y))
+      when (> tree-height maxh)
+        do (setf (aref visibility-mask (funcall location x y)) t))
+    ;; bottom watch
+    (loop
+      for y downfrom (1- height) to 0
+      for maxh = -1 then (max maxh tree-height)
+      for tree-height = (aref forest-arr (funcall location x y))
+      when (> tree-height maxh)
+        do (setf (aref visibility-mask (funcall location x y)) t)))
+
+  (loop for v across visibility-mask counting v))