Day 2: Dive!

Setup

Mix.install([
  {:kino, "~> 0.4.1"}
])

:ok

Input

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

Part 1

Kino.Input.read(input)
|> String.split("\n", trim: true)
|> Enum.map(&String.split(&1, " "))
|> Enum.split_with(fn [action, _] ->
  case action do
    "forward" -> true
    _ -> false
  end
end)
|> then(fn {l, r} ->
  {
    Enum.map(l, fn [_, v] -> String.to_integer(v) end),
    Enum.map(r, fn [action, v] ->
      case action do
        "up" -> String.to_integer(v) * -1
        "down" -> String.to_integer(v)
      end
    end)
  }
end)
|> then(fn {l, r} -> Enum.sum(l) * Enum.sum(r) end)

1670340

Part 2

Kino.Input.read(input)
|> String.split("\n", trim: true)
|> Enum.map(&String.split(&1, " "))
|> Enum.map(fn [action, v] ->
  v = String.to_integer(v)

  case action do
    "up" -> [0, -v, 0]
    "down" -> [0, v, 0]
    "forward" -> [v, 0, v]
  end
end)
|> Enum.reduce({0, 0, 0}, fn [h, a, d], {acc_h, acc_a, acc_d} ->
  {
    acc_h + h,
    acc_a + a,
    acc_d + d * (acc_a + a)
  }
end)
|> then(fn {x, _, y} -> x * y end)

1954293920