Nobody’s doing Advent of Code this year?

I might do the first week or so.

For Day 1, first I solved it using regular expressions and String.replace, which took about 10ms for each part.

Then I rewrote it using binaries and recursion, which got each part under 1ms.

  def filter_digits2(<<>>), do: <<>>
  def filter_digits2(<<x, rest::binary>>) when x in ?1..?9, do: <<x>> <> filter_digits2(rest)
  def filter_digits2(<<"one", rest::binary>>), do: "1" <> filter_digits2("e" <> rest)
  def filter_digits2(<<"two", rest::binary>>), do: "2" <> filter_digits2("o" <> rest)
  def filter_digits2(<<"three", rest::binary>>), do: "3" <> filter_digits2("e" <> rest)
  def filter_digits2(<<"four", rest::binary>>), do: "4" <> filter_digits2("r" <> rest)
  def filter_digits2(<<"five", rest::binary>>), do: "5" <> filter_digits2("e" <> rest)
  def filter_digits2(<<"six", rest::binary>>), do: "6" <> filter_digits2("x" <> rest)
  def filter_digits2(<<"seven", rest::binary>>), do: "7" <> filter_digits2("n" <> rest)
  def filter_digits2(<<"eight", rest::binary>>), do: "8" <> filter_digits2("t" <> rest)
  def filter_digits2(<<"nine", rest::binary>>), do: "9" <> filter_digits2("e" <> rest)
  def filter_digits2(<<_, rest::binary>>), do: filter_digits2(rest)

https://git.adamu.jp/adam/AdventOfCode/src/branch/main/2023/day1.exs