Day 4; run watches in a seperate process to allow continuation after crashes

lib/day4.ex

@@ -0,0 +1,39 @@
+defmodule Aoc2023.Day4 do
+  use Aoc2023
+
+  defp numbers(values) do
+    values |> String.split() |> Enum.map(&String.to_integer/1) |> MapSet.new()
+  end
+
+  def parse(input) do
+    input
+    |> lines
+    |> Enum.map(
+      &Regex.run(~r/Card\s+(?<id>\d+): (?<winning>(\s*\d+)+) \| (?<values>(\s*\d+)+)/, &1,
+        capture: ["id", "winning", "values"]
+      )
+    )
+    |> Enum.map(fn [id, winning, values] ->
+      {String.to_integer(id),
+       MapSet.intersection(numbers(winning), numbers(values)) |> MapSet.size()}
+    end)
+  end
+
+  def part1(input) do
+    for {_, count} <- input,
+        count > 0 do
+      2 ** (count - 1)
+    end
+    |> Enum.sum()
+  end
+
+  def part2(input) do
+    for {id, count} <- input,
+        id_ <- (id + 1)..(id + count)//1,
+        reduce: input |> Enum.map(elem(0) &&& const(1)) |> Enum.into(%{}) do
+      acc -> Map.update!(acc, id_, &(&1 + Map.get(acc, id)))
+    end
+    |> Enum.map(pipe(elem(1)))
+    |> Enum.sum()
+  end
+end