From 3fc130038785b9fb69148fa1c37b9e96a06a7fd4 Mon Sep 17 00:00:00 2001
From: bluepython508 <bluepython508@users.noreply.github.io>
Date: Sat, 16 Dec 2023 08:51:08 +0000
Subject: [PATCH] Day 16

---
 lib/day16.ex     | 71 ++++++++++++++++++++++++++++++++++++++++++++++++
 lib/mix_tasks.ex |  1 +
 tests/day16/1    | 10 +++++++
 tests/day16/1.1  |  1 +
 tests/day16/1.2  |  1 +
 5 files changed, 84 insertions(+)
 create mode 100644 lib/day16.ex
 create mode 100644 tests/day16/1
 create mode 100644 tests/day16/1.1
 create mode 100644 tests/day16/1.2

diff --git a/lib/day16.ex b/lib/day16.ex
new file mode 100644
index 0000000..c141220
--- /dev/null
+++ b/lib/day16.ex
@@ -0,0 +1,71 @@
+defmodule Aoc2023.Day16 do
+  use Aoc2023
+
+  defp emissions(char, dir) do
+    case {char, dir} do
+      {?., dir} -> [dir]
+      {?-, {0, dir}} -> [{0, dir}]
+      {?-, {_, 0}} -> [{0, -1}, {0, 1}]
+      {?|, {dir, 0}} -> [{dir, 0}]
+      {?|, {0, _}} -> [{-1, 0}, {1, 0}]
+      {?/, {dir, 0}} -> [{0, -dir}]
+      {?/, {0, dir}} -> [{-dir, 0}]
+      {?\\, {dir, 0}} -> [{0, dir}]
+      {?\\, {0, dir}} -> [{dir, 0}]
+    end
+  end
+
+  defp add_vec({y, x}, {y_, x_}) do
+    {y + y_, x + x_}
+  end
+
+  def parse(input) do
+    input
+    |> lines
+    |> Enum.map(&String.to_charlist/1)
+    |> Enum.with_index()
+    |> Enum.flat_map(fn {row, y} ->
+      row |> Enum.with_index() |> Enum.map(fn {c, x} -> {{y, x}, c} end)
+    end)
+    |> Enum.into(%{})
+  end
+
+  defp run(input, heads) do
+    loop = fn recur, energized, heads ->
+      energized_ = MapSet.union(energized, heads |> MapSet.new())
+
+      heads_ =
+        heads
+        |> Enum.flat_map(fn {coord, dir} ->
+          char = Map.get(input, coord)
+
+          if char,
+            do:
+              emissions(char, dir)
+              |> Enum.map(&{add_vec(coord, &1), &1})
+              |> Enum.reject(&MapSet.member?(energized_, &1))
+              |> Enum.filter(&Map.has_key?(input, elem(&1, 0))),
+            else: []
+        end)
+
+      if length(heads_) > 0, do: recur.(recur, energized_, heads_), else: energized_
+    end
+
+    loop.(loop, MapSet.new(), heads) |> Enum.map(pipe(elem(0))) |> MapSet.new() |> MapSet.size()
+  end
+
+  def part1(input) do
+    run(input, [{{0, 0}, {0, 1}}])
+  end
+
+  def part2(input) do
+    {my, mx} = input |> Enum.map(pipe(elem(0))) |> Enum.max()
+
+    [
+      0..my |> Enum.map(&{{&1, 0}, {0, 1}}),
+      0..my |> Enum.map(&{{&1, mx}, {0, -1}}),
+      0..mx |> Enum.map(&{{0, &1}, {1, 0}}),
+      0..mx |> Enum.map(&{{my, &1}, {-1, 0}})
+    ] |> Enum.concat |> Enum.map(&run(input, [&1])) |> Enum.max
+  end
+end
diff --git a/lib/mix_tasks.ex b/lib/mix_tasks.ex
index e0ab6f2..6b2299d 100644
--- a/lib/mix_tasks.ex
+++ b/lib/mix_tasks.ex
@@ -17,6 +17,7 @@ defmodule Mix.Tasks.Aoc do
   defp module(13), do: Aoc2023.Day13
   defp module(14), do: Aoc2023.Day14
   defp module(15), do: Aoc2023.Day15
+  defp module(16), do: Aoc2023.Day16
   # [MODULE INSERTION POINT]  
 
   defp base_dir(), do: System.get_env("AOC_BASE")
diff --git a/tests/day16/1 b/tests/day16/1
new file mode 100644
index 0000000..d6805ce
--- /dev/null
+++ b/tests/day16/1
@@ -0,0 +1,10 @@
+.|...\....
+|.-.\.....
+.....|-...
+........|.
+..........
+.........\
+..../.\\..
+.-.-/..|..
+.|....-|.\
+..//.|....
diff --git a/tests/day16/1.1 b/tests/day16/1.1
new file mode 100644
index 0000000..abc4eff
--- /dev/null
+++ b/tests/day16/1.1
@@ -0,0 +1 @@
+46
\ No newline at end of file
diff --git a/tests/day16/1.2 b/tests/day16/1.2
new file mode 100644
index 0000000..7003e7f
--- /dev/null
+++ b/tests/day16/1.2
@@ -0,0 +1 @@
+51
\ No newline at end of file