AoC 2023 - Day 1

Mix.install([:kino])

Section

input = Kino.Input.textarea("enter your input")

Part 1

defmodule Aoc.Day1.Part1 do
  def line_to_only_first_and_last_number(line) do
    line
    |> String.split("", trim: true)
    |> Enum.filter(fn char ->
      case Integer.parse(char) do
        {_, ""} -> true
        _ -> false
      end
    end)
    |> then(fn val ->
      [first | _] = val
      last = List.last(val)
      "#{first}#{last}"
    end)
  end
end

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  Aoc.Day1.Part1.line_to_only_first_and_last_number(line)
end)
|> Enum.map(fn val ->
  {num, ""} = Integer.parse(val)
  num
end)
|> Enum.sum()

Part 2

defmodule Aoc.Day1.Part2 do
  def parse_line(line) do
    replace_numbers(line)
  end

  # Apparently, if there is a number line oneight, we need to do 1 and 8.
  # At least, that's what lead me to the right solution.
  defp replace_numbers("one" <> rest), do: "1" <> replace_numbers("e" <> rest)
  defp replace_numbers("two" <> rest), do: "2" <> replace_numbers("o" <> rest)
  defp replace_numbers("three" <> rest), do: "3" <> replace_numbers("e" <> rest)
  defp replace_numbers("four" <> rest), do: "4" <> replace_numbers("r" <> rest)
  defp replace_numbers("five" <> rest), do: "5" <> replace_numbers("e" <> rest)
  defp replace_numbers("six" <> rest), do: "6" <> replace_numbers("x" <> rest)
  defp replace_numbers("seven" <> rest), do: "7" <> replace_numbers("n" <> rest)
  defp replace_numbers("eight" <> rest), do: "8" <> replace_numbers("t" <> rest)
  defp replace_numbers("nine" <> rest), do: "9" <> replace_numbers("e" <> rest)
  defp replace_numbers(<>), do: <> <> replace_numbers(rest)
  defp replace_numbers(""), do: ""
end

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  Aoc.Day1.Part2.parse_line(line)
end)
|> Enum.map(fn line ->
  Aoc.Day1.Part1.line_to_only_first_and_last_number(line)
end)
|> Enum.map(fn val ->
  {num, ""} = Integer.parse(val)
  num
end)
|> Enum.sum()