Advent of Code 2024 - Day 14

Mix.install([{:kino, github: "livebook-dev/kino"}])

kino_input = Kino.Input.textarea("Please paste your input file: ")

Part 1

input = Kino.Input.read(kino_input)

max_x = 101
max_y = 103
steps = 100

x = input
|> String.split("\n", trim: true)
|> Enum.map(fn robot_info ->
  Regex.scan(~r/-?\d+/, robot_info)
  |> Enum.map(&String.to_integer(hd(&1)))
end)
|> Enum.reduce([], fn [x, y, vx, vy], acc ->
  final_x = Integer.mod(x + vx * steps, max_x)
  final_y = Integer.mod(y + vy * steps, max_y)

  [{final_x, final_y} | acc]
end)
|> Enum.reduce({0, 0, 0, 0}, fn {x, y}, {q1, q2, q3, q4} ->
  mid_x = div(max_x, 2)
  mid_y = div(max_y, 2)

  cond do
    x < mid_x and y < mid_y -> {q1 + 1, q2, q3, q4}
    x < mid_x and y > mid_y -> {q1, q2 + 1, q3, q4}
    x > mid_x and y < mid_y -> {q1, q2, q3 + 1, q4}
    x > mid_x and y > mid_y -> {q1, q2, q3, q4 + 1}
    true -> {q1, q2, q3, q4}
  end
end)
|> Tuple.product()

Part 2

# Need to run this part in IEx
input = Kino.Input.read(kino_input)

max_x = 101
max_y = 103
steps = 100

# stole idea from https://git.adamu.jp/adam/AdventOfCode/src/branch/main/2024/day14.exs
defmodule TreeChecker do
  def find_tree(positions, max_x, max_y, count \\ 27, acc \\ 27) do
    positions = step(positions, max_x, max_y, count)
    positions_map = MapSet.new(positions, fn [x, y, _, _] -> {x, y} end)
    
    for y <- 0..(max_y - 1) do
      for x <- 0..(max_x - 1) do
        if MapSet.member?(positions_map, {x, y}) do
          IO.write("X")
        else
          IO.write(" ")
        end
      end

      IO.puts("|")
    end

    line = IO.gets("#{acc} tree? [y/N]?")

    if line |> String.trim() |> String.downcase() == "y" do
      acc
    else
      find_tree(positions, max_x, max_y, 101, acc + 101)
    end
  end

  defp step(positions, max_x, max_y, steps) do
    Enum.map(positions, fn [x, y, vx, vy] ->
      final_x = Integer.mod(x + vx * steps, max_x)
      final_y = Integer.mod(y + vy * steps, max_y)

      [final_x, final_y, vx, vy]
    end)
  end
end

input
|> String.split("\n", trim: true)
|> Enum.map(fn robot_info ->
  Regex.scan(~r/-?\d+/, robot_info)
  |> Enum.map(&amp;String.to_integer(hd(&amp;1)))
end)
|> TreeChecker.find_tree(max_x, max_y)