advent_of_code/elixir/livebook/2024/day3.livemd

AOC 2024 Day 3

Section

input = File.read!("/data/input.txt")

Regex.scan(
  ~r/mul\((\d+),(\d+)\)/,
  input
)
|> Stream.map(fn [_, a, b] -> String.to_integer(a) * String.to_integer(b) end)
|> Enum.sum()

for instruction <- Regex.scan(
  ~r/(mul\((\d+),(\d+)\)|don't\(\)|do\(\))/,
  input
), reduce: {true, 0} do
  {enabled?, acc} ->
    case {enabled?, instruction} do
      {false, ["mul" <> _ | _]} -> {false, acc}
      {true, ["mul" <> _, _, a, b]} -> {true, acc + String.to_integer(a) * String.to_integer(b)}
      {_, ["don" <> _ | _]} -> {false, acc}
      {_, ["do()" | _]} -> {true, acc}
    end
end