Untitled notebook

Section

defmodule Advent1 do
  def solve do
    File.stream!("#{File.cwd!()}/input/14_example.txt")
    |> Stream.map(&String.trim/1)
    |> Stream.map(&String.split/1)
    |> extract_koords_cave()

    # |> IO.inspect(label: "cave coords")
  end

  # the cave is filled with paths of stones  

  def extract_koords_cave(paths) do
    paths
    |> Stream.map(&Advent1.extract_coords_path/1)
    # |> IO.inspect(label: "path coords")
    |> Enum.reduce(&MapSet.union/2)
  end

  # one line of input describes one path  

  def extract_coords_path(path) do
    path
    |> Stream.filter(fn x -> x != "->" end)
    |> Stream.map(fn x -> String.split(x, ",") end)
    |> Stream.map(fn [x, y] -> [String.to_integer(x), String.to_integer(y)] end)
    |> Stream.map(fn [x, y] -> {x, y} end)
    |> Stream.chunk_every(2, 1, :discard)
    # |> (Enum.to_list() |> IO.inspect(label: "edges"))
    |> Stream.map(&extract_coords_edge/1)
    # |> (Enum.to_list() |> IO.inspect(label: "edges coords"))
    |> Enum.reduce(&MapSet.union/2)
  end

  # one path is composed of one or more edges

  def extract_coords_edge(edge) do
    [node_start, node_end] = edge
    extract_coords_nodes(node_start, node_end)
  end

  # one edge is described by exactly two nodes: node_start, node_end
  def extract_coords_nodes({x1, same}, {x2, same}) do
    Enum.to_list(x2..x1)
    |> Stream.map(fn x -> {x, same} end)
    |> MapSet.new()
  end

  def extract_coords_nodes({same, y1}, {same, y2}) do
    Enum.to_list(y2..y1)
    |> Stream.map(fn y -> {same, y} end)
    |> MapSet.new()
  end
end

Advent1.solve()

MapSet.new([
  {494, 9},
  {495, 9},
  {496, 6},
  {496, 9},
  {497, 6},
  {497, 9},
  {498, 4},
  {498, 5},
  {498, 6},
  {498, 9},
  {499, 9},
  {500, 9},
  {501, 9},
  {502, 4},
  {502, 5},
  {502, 6},
  {502, 7},
  {502, 8},
  {502, 9},
  {503, 4}
])