Advent of Code - Day 13

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)

input
|> String.split("\n\n", trim: true)
|> Enum.map(fn machines -> 
  Regex.scan(~r/\d+/, machines)
  |> Enum.map(&String.to_integer(hd(&1)))
  |> then(fn [ax, ay, bx, by, target_x, target_y] ->
    a_button_presses = (target_x * by - target_y * bx) / (ax * by - ay * bx)
    b_button_presses = (target_x - ax * a_button_presses) / bx
  
    [a_button_presses, b_button_presses]
    |> Enum.filter(fn num -> num == trunc(num) end)
  end)
end)
|> Enum.reject(&(&1 == []))
|> Enum.map(&List.to_tuple/1)
|> Enum.reduce(0, fn {a_button_presses, b_button_presses}, sum ->
  sum + a_button_presses * 3 + b_button_presses
end)
|> trunc()

Part 2

input = Kino.Input.read(kino_input)

input
|> String.split("\n\n", trim: true)
|> Enum.map(fn machines -> 
  Regex.scan(~r/\d+/, machines)
  |> Enum.map(&String.to_integer(hd(&1)))
  |> then(fn [ax, ay, bx, by, target_x, target_y] ->
    target_x = target_x + 10000000000000
    target_y = target_y + 10000000000000
    
    a_button_presses = (target_x * by - target_y * bx) / (ax * by - ay * bx)
    b_button_presses = (target_x - ax * a_button_presses) / bx
  
    [a_button_presses, b_button_presses]
  end)
end)
|> Enum.filter(fn [num_a, num_b] -> num_a == trunc(num_a) && num_b == trunc(num_b) end)
|> Enum.map(&List.to_tuple/1)
|> Enum.reduce(0, fn {a_button_presses, b_button_presses}, sum ->
  sum + a_button_presses * 3 + b_button_presses
end)
|> trunc()