From f2abc065ad615931431025290f0753bdd9614775 Mon Sep 17 00:00:00 2001
From: Felix Van der Jeugt <felix.vanderjeugt@posteo.net>
Date: Sun, 5 Dec 2021 10:11:11 +0100
Subject: [PATCH] day 5

---
 day05/part1.lua | 41 +++++++++++++++++++++++++++++++++++++++++
 day05/part2.lua | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 day05/part1.lua
 create mode 100644 day05/part2.lua

diff --git a/day05/part1.lua b/day05/part1.lua
new file mode 100644
index 0000000..2f9dfcc
--- /dev/null
+++ b/day05/part1.lua
@@ -0,0 +1,41 @@
+function readline()
+	local x1 = io.read("*n")
+	io.read(1) -- ","
+	local y1 = io.read("*n")
+	io.read(4) -- " -> "
+	local x2 = io.read("*n")
+	io.read(1) -- ","
+	local y2 = io.read("*n")
+	io.read("*l") -- "...\n"
+	return x1, y1, x2, y2
+end
+
+io.input(arg[3])
+local x1, y1, x2, y2 = readline()
+local field = {}
+while x1 ~= nil do
+	if x1 == x2 then
+		for y = math.min(y1, y2), math.max(y1, y2) do
+			local row = field[x1] or {}
+			row[y] = (row[y] or 0) + 1
+			field[x1] = row
+		end
+	elseif y1 == y2 then
+		for x = math.min(x1, x2), math.max(x1, x2) do
+			local row = field[x] or {}
+			row[y1] = (row[y1] or 0) + 1
+			field[x] = row
+		end
+	end
+	x1, y1, x2, y2 = readline()
+end
+
+local count = 0
+for r, row in pairs(field) do
+	for c, col in pairs(row) do
+		if col >= 2 then
+			count = count + 1
+		end
+	end
+end
+print(count)
diff --git a/day05/part2.lua b/day05/part2.lua
new file mode 100644
index 0000000..2c4328d
--- /dev/null
+++ b/day05/part2.lua
@@ -0,0 +1,48 @@
+function readline()
+	local x1 = io.read("*n")
+	io.read(1) -- ","
+	local y1 = io.read("*n")
+	io.read(4) -- " -> "
+	local x2 = io.read("*n")
+	io.read(1) -- ","
+	local y2 = io.read("*n")
+	io.read("*l") -- "...\n"
+	return x1, y1, x2, y2
+end
+
+function mark(field, x, y, count, dx, dy)
+	local i = 0
+	while i <= count do
+		local row = field[x+i*dx] or {}
+		row[y+i*dy] = (row[y+i*dy] or 0) + 1
+		field[x+i*dx] = row
+		i = i + 1
+	end
+end
+
+io.input(arg[3])
+local x1, y1, x2, y2 = readline()
+local field = {}
+while x1 ~= nil do
+	local x, y, count, dx, dy
+	if x1 == x2 then
+		mark(field, x1, math.min(y1, y2), math.abs(y1 - y2), 0, 1)
+	elseif y1 == y2 then
+		mark(field, math.min(x1, x2), y1, math.abs(x2 - x1), 1, 0)
+	elseif x1 + y1 == x2 + y2 then
+		mark(field, math.min(x1, x2), math.max(y1, y2), math.abs(x1 - x2), 1, -1)
+	else
+		mark(field, math.min(x1, x2), math.min(y1, y2), math.abs(x1 - x2), 1, 1)
+	end
+	x1, y1, x2, y2 = readline()
+end
+
+local count = 0
+for r, row in pairs(field) do
+	for c, col in pairs(row) do
+		if col >= 2 then
+			count = count + 1
+		end
+	end
+end
+print(count)