Day 18

Mix.install([
  {:kino, "~> 0.11.3"}
])

Section

input = """
R 6 (#70c710)
D 5 (#0dc571)
L 2 (#5713f0)
D 2 (#d2c081)
R 2 (#59c680)
D 2 (#411b91)
L 5 (#8ceee2)
U 2 (#caa173)
L 1 (#1b58a2)
U 2 (#caa171)
R 2 (#7807d2)
U 3 (#a77fa3)
L 2 (#015232)
U 2 (#7a21e3)
"""

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

defmodule Sol18 do
  def read(text) do
    for row <- String.split(text, "\n") do
      [dir, steps, color] = String.split(row, " ")
      [dir, String.to_integer(steps), color]
    end
  end

  def add_wall({row, col}, "R", steps) do
    for c <- 1..steps do
      {row, col + c}
    end
  end

  def add_wall({row, col}, "D", steps) do
    for r <- 1..steps do
      {row + r, col}
    end
  end

  def add_wall({row, col}, "U", steps) do
    for r <- 1..steps do
      {row - r, col}
    end
  end

  def add_wall({row, col}, "L", steps) do
    for c <- 1..steps do
      {row, col - c}
    end
  end

  def build(_, [], maze) do
    maze
  end

  def build({row, col}, [[dir, steps, _] | tail], maze) do
    # IO.inspect({{row, col}, [dir, steps]})
    case dir do
      "R" -> Sol18.build({row, col + steps}, tail, maze ++ Sol18.add_wall({row, col}, dir, steps))
      "U" -> Sol18.build({row - steps, col}, tail, maze ++ Sol18.add_wall({row, col}, dir, steps))
      "D" -> Sol18.build({row + steps, col}, tail, maze ++ Sol18.add_wall({row, col}, dir, steps))
      "L" -> Sol18.build({row, col - steps}, tail, maze ++ Sol18.add_wall({row, col}, dir, steps))
    end
  end

  def count([], _, _, score) do
    score
  end

  def count([{row, col} | tail], {lastr, lastc}, inside, score) do
    IO.inspect({{lastr, lastc}, {row, col}, inside, score})

    case {lastr == row, inside} do
      {false, _} ->
        IO.inspect("change row + 1")
        Sol18.count(tail, {row, col}, true, score + 1)

      {true, true} ->
        IO.inspect({"inside + ", col - lastc})

        Sol18.count(
          tail,
          {row, col},
          if lastc + 1 == col do
            inside
          else
            not inside
          end,
          score + col - lastc
        )

      {true, false} ->
        IO.inspect({"outside + 1"})

        Sol18.count(
          tail,
          {row, col},
          if lastc + 1 == col do
            inside
          else
            not inside
          end,
          score + 1
        )
    end
  end
end

input_data = Kino.Input.read(input)
cmds = Sol18.read(String.trim(input_data))
sharps = Sol18.build({0, 0}, cmds, [{0, 0}])
Sol18.count(Enum.dedup(Enum.sort(sharps)), {0, -1}, true, 0)