Day 4

Mix.install([
  {:req, "~> 0.3.2"},
  {:vega_lite, "~> 0.1.6"},
  {:kino_vega_lite, "~> 0.1.6"}
])

alias VegaLite, as: Vl

aoc_session = System.fetch_env!("LB_AOC_SESSION")
input_url = "https://adventofcode.com/2022/day/4/input"
{:ok, %{body: input}} = Req.get(input_url, headers: [cookie: "session=#{aoc_session}"])

Input

test_input = """
2-4,6-8
2-3,4-5
5-7,7-9
2-8,3-7
6-6,4-6
2-6,4-8
"""

Part 1

parse_row = fn row_str ->
  [a1, a2, b1, b2] =
    ~r/([0-9]+)-([0-9]+),([0-9]+)-([0-9]+)/
    |> Regex.run(row_str)
    |> Enum.drop(1)
    |> Enum.map(&String.to_integer/1)

  {MapSet.new(a1..a2), MapSet.new(b1..b2)}
end

input
|> String.split("\n", trim: true)
|> Enum.count(fn str ->
  {range_a, range_b} = parse_row.(str)
  MapSet.subset?(range_a, range_b) or MapSet.subset?(range_b, range_a)
end)

Part 2

input
|> String.split("\n", trim: true)
|> Enum.count(fn str ->
  {range_a, range_b} = parse_row.(str)
  not MapSet.disjoint?(range_a, range_b)
end)