AOC 2023 - Day 1

Mix.install([
  {:kino_aoc, "~> 0.1"}
])

Input

{:ok, puzzle_input} =
  KinoAOC.download_puzzle("2023", "1", System.fetch_env!("LB_AOC_SESSION"))

Part 1 - Solution

puzzle_input
|> String.split()
|> Enum.reduce(0, fn line, acc ->
  numbers =
    line
    |> String.replace(~r/[^\d]/, "")

  calibration_value =
    "#{String.at(numbers, 0)}#{String.at(numbers, -1)}"
    |> String.to_integer()

  acc + calibration_value
end)

Part 2 - Solution

defmodule Day1Part2 do
  def starts_with_number("one" <> _rem), do: {"1", true}
  def starts_with_number("two" <> _rem), do: {"2", true}
  def starts_with_number("three" <> _rem), do: {"3", true}
  def starts_with_number("four" <> _rem), do: {"4", true}
  def starts_with_number("five" <> _rem), do: {"5", true}
  def starts_with_number("six" <> _rem), do: {"6", true}
  def starts_with_number("seven" <> _rem), do: {"7", true}
  def starts_with_number("eight" <> _rem), do: {"8", true}
  def starts_with_number("nine" <> _rem), do: {"9", true}
  def starts_with_number("1" <> _rem), do: {"1", true}
  def starts_with_number("2" <> _rem), do: {"2", true}
  def starts_with_number("3" <> _rem), do: {"3", true}
  def starts_with_number("4" <> _rem), do: {"4", true}
  def starts_with_number("5" <> _rem), do: {"5", true}
  def starts_with_number("6" <> _rem), do: {"6", true}
  def starts_with_number("7" <> _rem), do: {"7", true}
  def starts_with_number("8" <> _rem), do: {"8", true}
  def starts_with_number("9" <> _rem), do: {"9", true}
  def starts_with_number(string), do: {string, false}

  def string_to_numbers(line) do
    Enum.reduce(0..(String.length(line) - 1), "", fn idx, acc ->
      {_start, remainder} = String.split_at(line, idx)
      {number, match_found} = starts_with_number(remainder)
      if match_found, do: acc <> number, else: acc
    end)
  end
end

puzzle_input
|> String.split()
|> Enum.map(fn line ->
  numbers_string =
    Day1Part2.string_to_numbers(line)
    |> String.replace(~r/[^\d]/, "")

  "#{String.at(numbers_string, 0)}#{String.at(numbers_string, -1)}"
  |> String.to_integer()
end)
|> Enum.sum()