From 2ab4d1c439afac70fe7debac06531e6c01df25be Mon Sep 17 00:00:00 2001
From: Adam Millerchip <adam@millerchip.net>
Date: Thu, 1 Dec 2022 23:54:32 +0900
Subject: [PATCH] 2022 day1

---
 2022/day1.exs | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 2022/day1.exs

diff --git a/2022/day1.exs b/2022/day1.exs
new file mode 100644
index 0000000..7974dd5
--- /dev/null
+++ b/2022/day1.exs
@@ -0,0 +1,58 @@
+defmodule Day1 do
+  def part1(input) do
+    input
+    |> Enum.map(&Enum.sum/1)
+    |> Enum.max()
+  end
+
+  def part2(input) do
+    input
+    |> Enum.map(&Enum.sum/1)
+    |> Enum.sort(:desc)
+    |> Enum.take(3)
+    |> Enum.sum()
+  end
+
+  def input do
+    with [input_filename] <- System.argv(),
+         {:ok, input} <- File.read(input_filename) do
+      input
+      |> String.split("\n\n")
+      |> Enum.map(&for elf <- String.split(&1, "\n", trim: true), do: String.to_integer(elf))
+    else
+      _ -> :error
+    end
+  end
+
+  #######################
+  # HERE BE BOILERPLATE #
+  #######################
+
+  def run do
+    case input() do
+      :error -> print_usage()
+      input -> run_parts_with_timer(input)
+    end
+  end
+
+  defp run_parts_with_timer(input) do
+    run_with_timer(1, fn -> part1(input) end)
+    run_with_timer(2, fn -> part2(input) end)
+  end
+
+  defp run_with_timer(part, fun) do
+    {time, result} = :timer.tc(fun)
+    IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
+    IO.puts("#{result}\n")
+  end
+
+  defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
+  defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
+  defp format_time(μsec), do: "#{μsec / 1_000_000}s"
+
+  defp print_usage do
+    IO.puts("Usage: elixir day1.exs input_filename")
+  end
+end
+
+Day1.run()