Advent of Code 2022 - Day 6

Mix.install([
  {:req_aoc, github: "mcrumm/req_aoc", ref: "eef58c9"}
])

Puzzle description

Day 6: Tuning Trouble.

Solution

defmodule Part1 do
  # preflight:
  ## split string into lines (without break characters)
  def run(input) do
    ###
    input |> String.trim_leading("\n") |> run(0, [])
  end

  defp run(<>, index, []) do
    run(input, index + 1, [char])
  end

  defp run(<>, index, chars) when length(chars) < 4 do
    if char in chars do
      idx = Enum.find_index(chars, &amp;(&amp;1 == char))
      {_, new_chars} = Enum.split(chars, idx + 1)

      # restart with the current char
      run(input, index + 1, new_chars ++ [char])
    else
      run(input, index + 1, chars ++ [char])
    end
  end

  defp run(_, index, chars) do
    index
  end
end

defmodule Part2 do
  # preflight:
  ## split string into lines (without break characters)
  def run(input) do
    ###
    input |> String.trim_leading("\n") |> run(0, [])
  end

  defp run(<>, index, []) do
    run(input, index + 1, [char])
  end

  defp run(<>, index, chars) when length(chars) < 14 do
    if char in chars do
      idx = Enum.find_index(chars, &amp;(&amp;1 == char))
      {_, new_chars} = Enum.split(chars, idx + 1)

      # restart with the current char
      run(input, index + 1, new_chars ++ [char])
    else
      run(input, index + 1, chars ++ [char])
    end
  end

  defp run(_, index, chars) do
    index
  end
end

ExUnit.start(autorun: false)

defmodule Test do
  use ExUnit.Case, async: true

  @input System.fetch_env!("LB_AOC_SESSION") |> ReqAOC.fetch!({2022, 06}, max_retries: 0)

  test "part 1" do
    assert "mjqjpqmgbljsphdztnvjfqwrcgsmlb" |> Part1.run() |> dbg() === 7
    assert "bvwbjplbgvbhsrlpgdmjqwftvncz" |> Part1.run() |> dbg() === 5
    assert "nppdvjthqldpwncqszvftbrmjlhg" |> Part1.run() |> dbg() === 6
    assert "nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg" |> Part1.run() |> dbg() === 10
    assert "zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw" |> Part1.run() |> dbg() === 11

    @input |> Part1.run() |> dbg()
  end

  test "part 2" do
    assert "mjqjpqmgbljsphdztnvjfqwrcgsmlb" |> Part2.run() |> dbg() === 19
    assert "bvwbjplbgvbhsrlpgdmjqwftvncz" |> Part2.run() |> dbg() === 23
    assert "nppdvjthqldpwncqszvftbrmjlhg" |> Part2.run() |> dbg() === 23
    assert "nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg" |> Part2.run() |> dbg() === 29
    assert "zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw" |> Part2.run() |> dbg() === 26

    @input |> Part2.run() |> dbg()
  end
end

ExUnit.configure(trace: true)
ExUnit.run()