Advent of Code 2024 - Day 01

Mix.install([
  {:req, "~> 0.5"},
  {:benchee, "~> 1.3"}
])

Input

opts = [headers: [{"cookie", "session=#{System.fetch_env!("LB_AOC_SESSION")}"}]]
puzzle_input = Req.get!("https://adventofcode.com/2024/day/1/input", opts).body

{left, right} =
  puzzle_input
  |> String.split("\n", trim: true)
  |> Enum.map(fn row ->
    row
    |> String.split()
    |> then(fn [l, r] -> {String.to_integer(l), String.to_integer(r)} end)
  end)
  |> Enum.unzip()

Puzzle 1

puzzle_1 = fn ->
  Enum.zip(Enum.sort(left), Enum.sort(right))
  |> Enum.map(fn {l, r} ->
    abs(l - r)
  end)
  |> Enum.sum()
end

puzzle_1.()

Puzzle 2

puzzle_2 = fn ->
  frequencies = Enum.frequencies(right)
  
  left
  |> Enum.map(fn num ->
    Map.get(frequencies, num, 0) * num
  end)
  |> Enum.sum()
end

puzzle_2.()

Benchmarks

Benchee.run(
  %{
    "puzzle_1" => fn -> puzzle_1.() end,
    "puzzle_2" => fn -> puzzle_2.() end
  })