AoC 2024 - Day 2

Mix.install([
  {:kino, "~> 0.14.2"}
])

Setup

input = Kino.Input.textarea("Input text")

Part 1

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  line
  |> String.split(" ", trim: true)
  |> Enum.map(fn num ->
    String.to_integer(num)
  end)
  |> Enum.chunk_every(2, 1, :discard)
  |> Enum.map(fn [val1, val2] ->
    val1 - val2
  end)
end)
|> Enum.map(fn line ->
  safe_asc = line |> Enum.all?(fn num ->
    num > 0 and num <= 3
  end)
  safe_desc = line |> Enum.all?(fn num ->
    num < 0 and num >= -3
  end)

  safe_asc or safe_desc
end)
|> Enum.count(fn val -> val end)

Part 2

defmodule AoC2024.Day2 do
  def valid?([a, b | _]) when abs(b - a) not in [1, 2, 3], do: false
  def valid?([a, b | rest]), do: valid?([b | rest], b - a)
  def valid?([_], _dir), do: true

  def valid?([a, b | rest], dir) do
    new_dir = b - a
  
    if ((dir < 0 and new_dir < 0) or (dir > 0 and new_dir > 0)) and abs(new_dir) <= 3 do
      valid?([b | rest], new_dir)
    else
      false
    end
  end
end

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  line
  |> String.split(" ", trim: true)
  |> Enum.map(fn num ->
    String.to_integer(num)
  end)
end)
|> Enum.count(fn line ->
  Enum.find_value(0..(length(line) - 1), false, fn val ->
    line |> List.delete_at(val) |> AoC2024.Day2.valid?()
  end)
end)