From 65502255e3bc10558c43302319ac8129b1330fcb Mon Sep 17 00:00:00 2001
From: Oscar Najera <hi@oscarnajera.com>
Date: Fri, 9 Dec 2022 03:11:41 +0100
Subject: [AoC2022] Elisp 08

---
 AoC2022/08/solver.el | 123 +++++++++++++++++++++++++++++++++++----------------
 1 file changed, 84 insertions(+), 39 deletions(-)

(limited to 'AoC2022/08')

diff --git a/AoC2022/08/solver.el b/AoC2022/08/solver.el
index 9c19651..27ee8a0 100644
--- a/AoC2022/08/solver.el
+++ b/AoC2022/08/solver.el
@@ -14,50 +14,95 @@
 ;;  Day 08
 ;;
 ;;; Code:
+(cl-defstruct (forest (:constructor forest--create)
+                      (:copier nil))
+  "Contaner for the forest layout"
+  grid (width nil :read-only t) (depth nil :read-only t))
 
-(with-temp-buffer
-  (insert-file-contents "input")
-  (let* ((rows (split-string (buffer-string)))
-         (forest-depth (length rows))
-         (forest-width (length (car rows)))
-         (forest
-          (seq-mapcat
-           (lambda (row)
-             (cl-map 'vector (lambda (col) (logxor col 48)) row)) ;; 48 is the ascii 0
-           rows 'vector))
-         (visibility
-          (make-bool-vector (* forest-width forest-depth) nil))
-         (last-max -1))
+(defsubst forest-index (forest i j)
+  (+ j (* (forest-width forest) i)))
+
+(defun solver-tree-visibility (forest)
+  (let ((visibility
+         (forest--create
+          :grid (make-bool-vector (* (forest-width forest) (forest-depth forest)) nil)
+          :depth (forest-depth forest)
+          :width (forest-width forest)))
+        last-max)
     (cl-flet ((update-visibility (index)
-                                 (let ((tree-height (aref forest index))
-                                       (mask-val (aref visibility index)))
-                                   (setf (aref visibility index) (or mask-val (< last-max tree-height)))
+                                 (let ((tree-height (aref (forest-grid forest) index))
+                                       (mask-val (aref (forest-grid visibility) index)))
+                                   (setf (aref (forest-grid visibility) index) (or mask-val (< last-max tree-height)))
                                    (setq last-max (max last-max tree-height)))))
-
-
-      ;; left visible
-      (dotimes (i forest-width)
+      (dotimes (i (forest-depth forest))
+        ;; left visible
         (setq last-max -1)
-        (dotimes (j forest-depth)
-          (update-visibility (+ j (* forest-width i)))))
-      ;; top visible
-      (dotimes (j forest-depth)
+        (dotimes (j (forest-width forest))
+          (update-visibility (forest-index forest i j)))
+        ;; rigth visible
         (setq last-max -1)
-        (dotimes (i forest-width)
-          (update-visibility (+ j (* forest-width i)))))
-      ;; rigth visible
-      (dotimes (i forest-width)
+        (cl-loop for j downfrom (1- (forest-width forest)) to 0 do
+                 (update-visibility (forest-index forest i j))))
+      (dotimes (j (forest-width forest))
+        ;; top visible
         (setq last-max -1)
-        (cl-loop for j downfrom (1- forest-depth) to 0 do
-                 (update-visibility (+ j (* forest-width i)))))
-      ;; bottom visible
-      (dotimes (j forest-depth)
+        (dotimes (i (forest-depth forest))
+          (update-visibility (forest-index forest i j)))
+        ;; bottom visible
         (setq last-max -1)
-        (cl-loop for i downfrom (1- forest-width) to 0 do
-          (update-visibility (+ j (* forest-width i))))))
+        (cl-loop for i downfrom (1- (forest-depth forest)) to 0 do
+                 (update-visibility (forest-index forest i j)))))
+    visibility))
+
+(defun solver-parse-input ()
+  (with-temp-buffer
+    (insert-file-contents "input")
+    (let ((rows (split-string (buffer-string))))
+      (forest--create
+       :grid (seq-mapcat
+              (lambda (row)
+                (cl-map 'vector (lambda (col) (logxor col 48)) row)) ;; 48 is the ascii 0
+              rows 'vector)
+       :depth (length rows)
+       :width (length (car rows))))))
+
+(defun solver-max-view-score (forest)
+ (let ((score (forest--create
+                 :grid (make-vector (* (forest-width forest) (forest-depth forest)) 0)
+                 :depth (forest-depth forest)
+                 :width (forest-width forest))))
+    (dotimes (i (forest-depth forest))
+        (dotimes (j (forest-width forest))
+          (let ((tree-height (aref (forest-grid forest) (forest-index forest i j))))
+            (aset (forest-grid score) (forest-index score i j)
+                  (*
+                   ;; left
+                   (cl-loop for l from (1+ j) below (forest-width forest)
+                            for v-tree = (aref (forest-grid forest) (forest-index forest i l))
+                            count l
+                            until (>= v-tree tree-height))
+                   ;; right
+                   (cl-loop for l downfrom (1- j) to 0
+                            for v-tree = (aref (forest-grid forest) (forest-index forest i l))
+                            count l
+                            until (>= v-tree tree-height))
+                   ;; top
+                   (cl-loop for l downfrom (1- i) to 0
+                            for v-tree = (aref (forest-grid forest) (forest-index forest l j))
+                            count l
+                            until (>= v-tree tree-height))
+                   ;; bottom
+                   (cl-loop for l from (1+ i) below (forest-depth forest)
+                            for v-tree = (aref (forest-grid forest) (forest-index forest l j))
+                            count l
+                            until (>= v-tree tree-height)))))))
+    score))
 
-    (seq-partition
-     (cl-map 'vector #'identity
-             visibility) 5)
-    (cl-loop for v across visibility when v count it)
-    ))
+(ert-deftest test-solver ()
+  (let* ((forest (solver-parse-input))
+         (visibility (solver-tree-visibility forest)))
+    ;; part 1
+    (should (= 1672 (cl-loop for v across (forest-grid  visibility) when v count it)))
+    ;; part 2
+    (thread-first (solver-max-view-score forest) (forest-grid) (seq-max)
+                  (= 327180) (should))))
-- 
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