Advent of Code 2023 Day 8 Part 1

Mix.install([
  {:kino_aoc, "~> 0.1.5"}
])

Get Inputs

{:ok, puzzle_input} =
  KinoAOC.download_puzzle("2023", "8", System.fetch_env!("LB_SESSION"))

My answer

defmodule Resolver do
  def parse(input) do
    [instructions | maps] = String.split(input, "\n\n")

    instructions = String.codepoints(instructions)

    maps =
      maps
      |> hd()
      |> String.split("\n")
      |> Enum.into(%{}, fn line ->
        parse_map(line)
      end)

    {instructions, maps}
  end

  defp parse_map(line) do
    [current, left, right] =
      line
      |> String.replace("=", "")
      |> String.replace("(", "")
      |> String.replace(")", "")
      |> String.replace(",", "")
      |> String.split(" ", trim: true)

    {current, %{"L" => left, "R" => right}}
  end

  def resolve(instructions, maps) do
    step("AAA", maps, 0, instructions, 0)
  end

  defp step("ZZZ", _, _, _, acc), do: acc

  defp step(current, maps, inst_index, instructions, acc) do
    instruction = Enum.at(instructions, inst_index)

    next = maps[current][instruction]

    next_inst_index =
      if inst_index == Enum.count(instructions) - 1 do
        0
      else
        inst_index + 1
      end

    step(next, maps, next_inst_index, instructions, acc + 1)
  end
end

{instructions, maps} =
  """
  RL

  AAA = (BBB, CCC)
  BBB = (DDD, EEE)
  CCC = (ZZZ, GGG)
  DDD = (DDD, DDD)
  EEE = (EEE, EEE)
  GGG = (GGG, GGG)
  ZZZ = (ZZZ, ZZZ)
  """
  |> String.slice(0..-2)
  |> Resolver.parse()

Resolver.resolve(instructions, maps)

{instructions, maps} =
  """
  LLR

  AAA = (BBB, BBB)
  BBB = (AAA, ZZZ)
  ZZZ = (ZZZ, ZZZ)
  """
  |> String.slice(0..-2)
  |> Resolver.parse()

Resolver.resolve(instructions, maps)

{instructions, maps} = Resolver.parse(puzzle_input)

Resolver.resolve(instructions, maps)