Day 10

Section

defmodule Part1 do
  def example() do
    """
    .....
    .S-7.
    .|.|.
    .L-J.
    .....
    """
    |> String.split("\n", trim: true)
  end

  def mapping() do
    %{
      "|" => ["n", "s"],
      "-" => ["e", "w"],
      "L" => ["n", "e"],
      "J" => ["n", "w"],
      "7" => ["s", "w"],
      "F" => ["s", "e"]
    }
  end

  def get_starting_pos(list) do
    Enum.with_index(list)
    |> Enum.reduce_while({nil, nil}, fn {l, x}, acc ->
      if "S" in l do
        y = Enum.find_index(l, fn ll -> "S" == ll end)
        {:halt, {x, y}}
      else
        {:cont, acc}
      end
    end)
  end

  def get_path(list, curr \\ [])

  def get_path(list, []) do
    pos = get_starting_pos(list)
    get_path(list, [[{"S", pos}]])
  end

  def get_path(list, curr) do
    IO.inspect({"x", curr})

    if length(curr) == 3 do
      throw("...")
    end

    [first | _] = curr

    l =
      Enum.flat_map(first, fn {_, pos} ->
        next_pos(list, pos)
      end)

    get_path(list, [l | curr])
  catch
    _ -> nil
  end

  def next_pos(list, {x, y}) do
    [{x + 1, 1}, {x - 1, 1}, {x, y + 1}, {x, y - 1}]
    |> Enum.reject(fn {x, y} -> x < 0 || y < 0 end)
    |> Enum.map(fn {x, y} ->
      i =
        Enum.at(list, y)
        |> Enum.at(x)

      if i == "." do
        nil
      else
        {i, {x, y}}
      end
    end)
    |> Enum.reject(&amp;(&amp;1 == nil))
  end
end

list =
  Part1.example()
  |> Enum.map(fn i ->
    String.split(i, "", trim: true)
  end)

Part1.get_path(list)

x = 1
y = 1

[{x + 1, 1}, {x - 1, 1}, {x, y + 1}, {x, y - 1}]
|> Enum.reject(fn {x, y} -> x < 0 || y < 0 end)
|> Enum.map(fn {x, y} ->
  i =
    Enum.at(list, y)
    |> Enum.at(x)
    |> IO.inspect()

  if i == "." do
    nil
  else
    {i, {x, y}}
  end
end)
|> Enum.reject(&amp;(&amp;1 == nil))