🎄 Year 2024 🔔 Day 01

Section

steps =
  File.read!("#{__DIR__}/../../../inputs/2025/day01.txt")
  |> String.split("\n", trim: true)
  |> Enum.map(&String.split_at(&1, 1))
  |> Enum.map(fn {dir, n} -> {dir, String.to_integer(n)} end)

Part 1

Enum.scan(steps, 50, fn {dir, n}, acc ->
  new_n = if dir == "L", do: acc - n, else: acc + n
  new_n = Integer.mod(new_n, 100)
end)
|> Enum.count(&(&1 === 0))

Part 2

Enum.scan(steps, {0, 50}, fn {dir, n}, {_, acc} ->
  new_n = if dir == "L", do: acc - n, else: acc + n

  zero_count = div(abs(new_n), 100)
  zero_count = if new_n == 0, do: zero_count + 1, else: zero_count
  zero_count = if new_n < 0 &amp;&amp; acc > 0, do: zero_count + 1, else: zero_count

  new_n = Integer.mod(new_n, 100)

  {zero_count, new_n}
end)
|> Enum.map(&amp;elem(&amp;1, 0))
|> Enum.sum()