From ba515a6a1396f1f4932cbec80f0dc52caa761052 Mon Sep 17 00:00:00 2001
From: Justin Wernick <justin@worthe-it.co.za>
Date: Fri, 13 Sep 2024 15:49:18 +0200
Subject: Day 6

---
 2015/day6.exs | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 2015/day6.exs

(limited to '2015')

diff --git a/2015/day6.exs b/2015/day6.exs
new file mode 100644
index 0000000..9ad62cd
--- /dev/null
+++ b/2015/day6.exs
@@ -0,0 +1,87 @@
+instructions = File.stream!("inputs/day6.txt")
+
+regex = ~r/(toggle|turn off|turn on) ([0-9]+),([0-9]+) through ([0-9]+),([0-9]+)/
+
+endLights1 =
+  Enum.reduce(instructions, MapSet.new(), fn instruction, acc ->
+    [_, action, x1, y1, x2, y2] = Regex.run(regex, instruction)
+    {x1, ""} = Integer.parse(x1)
+    {x2, ""} = Integer.parse(x2)
+    {y1, ""} = Integer.parse(y1)
+    {y2, ""} = Integer.parse(y2)
+
+    case action do
+      "toggle" ->
+        for x <- x1..x2, y <- y1..y2, reduce: acc do
+          acc ->
+            if MapSet.member?(acc, {x, y}) do
+              MapSet.delete(acc, {x, y})
+            else
+              MapSet.put(acc, {x, y})
+            end
+        end
+
+      "turn off" ->
+        for x <- x1..x2, y <- y1..y2, reduce: acc do
+          acc -> MapSet.delete(acc, {x, y})
+        end
+
+      "turn on" ->
+        for x <- x1..x2, y <- y1..y2, reduce: acc do
+          acc -> MapSet.put(acc, {x, y})
+        end
+    end
+  end)
+
+litLights1 = MapSet.size(endLights1)
+
+IO.puts("Lit lights count 1: #{litLights1}")
+
+min = 0
+max = 999
+
+startLights2 =
+  for x <- min..max, y <- min..max, reduce: Map.new() do
+    acc -> Map.put(acc, {x, y}, 0)
+  end
+
+endLights2 =
+  Enum.reduce(instructions, startLights2, fn instruction, acc ->
+    [_, action, x1, y1, x2, y2] = Regex.run(regex, instruction)
+    {x1, ""} = Integer.parse(x1)
+    {x2, ""} = Integer.parse(x2)
+    {y1, ""} = Integer.parse(y1)
+    {y2, ""} = Integer.parse(y2)
+
+    case action do
+      "toggle" ->
+        for x <- x1..x2, y <- y1..y2, reduce: acc do
+          acc ->
+            {_, acc} = Map.get_and_update!(acc, {x, y}, fn i -> {i, i + 2} end)
+            acc
+        end
+
+      "turn off" ->
+        for x <- x1..x2, y <- y1..y2, reduce: acc do
+          acc ->
+            {_, acc} =
+              Map.get_and_update!(acc, {x, y}, fn
+                0 -> {0, 0}
+                i -> {i, i - 1}
+              end)
+
+            acc
+        end
+
+      "turn on" ->
+        for x <- x1..x2, y <- y1..y2, reduce: acc do
+          acc ->
+            {_, acc} = Map.get_and_update!(acc, {x, y}, fn i -> {i, i + 1} end)
+            acc
+        end
+    end
+  end)
+
+lightIntensity2 = Map.values(endLights2) |> Enum.sum()
+
+IO.puts("Lit lights intensity 2: #{lightIntensity2}")
-- 
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