Advent of Code 2022

Mix.install([
  {:req, "~> 0.3.2"}
])

Day 3

input =
  "https://adventofcode.com/2022/day/3/input"
  |> Req.get!(headers: [cookie: "session=#{System.get_env("AOC_COOKIE")}"])
  |> Map.get(:body)

Part 1

input
|> String.split("\n", trim: true)
|> Enum.map(fn s ->
  String.split_at(s, div(String.length(s), 2))
  |> Tuple.to_list()
  |> Enum.map(fn s ->
    String.split(s, "", trim: true)
    |> MapSet.new()
  end)
  |> Enum.reduce(fn s, acc ->
    MapSet.intersection(s, acc)
  end)
  |> MapSet.to_list()
  |> Enum.at(0)
  |> :binary.first()
  |> case do
    n when n >= 97 ->
      n - 96

    n ->
      n - 38
  end
end)
|> Enum.sum()

Part 2

input
|> String.split("\n", trim: true)
|> Enum.chunk_every(3)
|> Enum.map(fn groups ->
  groups
  |> Enum.map(fn g ->
    String.split(g, "", trim: true) |> MapSet.new()
  end)
  |> Enum.reduce(fn g, acc -> MapSet.intersection(acc, g) end)
  |> MapSet.to_list()
  |> Enum.at(0)
  |> :binary.first()
  |> case do
    n when n >= 97 ->
      n - 96

    n ->
      n - 38
  end
end)
|> Enum.sum()