From 3555be54c2abb8d5ece008a60dbdfbde0ffbddd7 Mon Sep 17 00:00:00 2001
From: Alex Pickering <alex@cogarr.net>
Date: Fri, 7 Feb 2025 12:49:48 -0600
Subject: inital commit

---
 08/1.lua | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 08/1.lua

(limited to '08/1.lua')

diff --git a/08/1.lua b/08/1.lua
new file mode 100644
index 0000000..326b8c4
--- /dev/null
+++ b/08/1.lua
@@ -0,0 +1,49 @@
+local heights = {}
+
+for line in io.lines() do
+	local trees = {}
+	line:gsub("%d",function(t)
+		local tree = {
+			height=tonumber(t),
+			visible={up=false,down=false,left=false,right=false},
+		}
+		table.insert(trees,tree) 
+	end)
+	table.insert(heights,trees)
+end
+local nrow,ncol = #heights, #heights[1]
+for i = 1,nrow do
+	heights[i][1].visible.left = true
+	heights[i][ncol].visible.right = true
+end
+for i = 1,ncol do
+	heights[1][i].visible.up = true
+	heights[nrow][i].visible.down = true
+end
+local total_visible = (nrow*2) + (ncol*2) - 4
+local directions = {up={1,0},down={-1,0},left={0,1},right={0,-1}}
+local function calc_visible(row,col)
+	local t = heights[row][col]
+	for name,direction in pairs(directions) do
+		local i,j = row - direction[1], col - direction[2]
+		while heights[i] and heights[i][j] do
+			if t.height > heights[i][j].height and heights[i][j].visible[name] then
+				t.visible[name] = true
+				break
+			elseif t.height <= heights[i][j].height then
+				t.visible[name] = false
+				break
+			end
+			i,j = i - direction[1], j - direction[2]
+		end
+	end
+	if t.visible.left or t.visible.right or t.visible.up or t.visible.down then
+		total_visible = total_visible + 1
+	end
+end
+for row = 2, nrow-1 do
+	for col = 2, ncol-1 do
+		calc_visible(row,col)
+	end
+end
+print(total_visible)
-- 
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