AOC 2022 14

1.exs

draw = fn paths, x, y, code ->
  put_in(paths, [Access.key(x, %{}), y], code) 
end

paths = 
  System.argv()
  |> List.first()
  |> File.stream!()
  |> Enum.reduce(%{}, fn path, paths -> 
    path
    |> String.split(" -> ", trim: true)
    |> Enum.map(fn node -> node |> String.trim() |> String.split(",") |> Enum.map(& String.to_integer/1) end)
    |> Enum.chunk_every(2, 1, :discard)
    |> Enum.reduce(paths, fn 
      [[x, from_y], [x, to_y]], paths -> Enum.reduce(from_y..to_y, paths, & draw.(&2, x, &1, "#"))
      [[from_x, y], [to_x, y]], paths -> Enum.reduce(from_x..to_x, paths, & draw.(&2, &1, y, "#"))
    end)
  end)
  
sand_fall = fn paths, {x, y}, self ->
  down_y = y + 1
  
  paths
  |> get_in([x, down_y])
  |> case do
    nil -> if y + 1 > paths |> Map.get(x, %{}) |> Map.keys() |> Enum.max(&>=/2, fn -> 0 end), do: :infinity, else: self.(paths, {x, down_y}, self)
    floor when floor in ["#", "o"] -> 
      cond do
        is_nil(get_in(paths, [x - 1, down_y])) -> self.(paths, {x - 1, down_y}, self)
        is_nil(get_in(paths, [x + 1, down_y])) -> self.(paths, {x + 1, down_y}, self)
        true -> draw.(paths, x, y, "o") 
      end
  end
end
  
Stream.iterate(1, & &1 + 1)
|> Enum.reduce_while(paths, fn unit, paths -> 
  paths
  |> sand_fall.({500, 0}, sand_fall)
  |> case do
    :infinity -> {:halt, unit}
    paths -> {:cont, paths}
  end
end)
|> IO.inspect

2.exs

draw = fn paths, x, y, code ->
  put_in(paths, [Access.key(x, %{}), y], code) 
end

paths = 
  System.argv()
  |> List.first()
  |> File.stream!()
  |> Enum.reduce(%{}, fn path, paths -> 
    path
    |> String.split(" -> ", trim: true)
    |> Enum.map(fn node -> node |> String.trim() |> String.split(",") |> Enum.map(& String.to_integer/1) end)
    |> Enum.chunk_every(2, 1, :discard)
    |> Enum.reduce(paths, fn 
      [[x, from_y], [x, to_y]], paths -> Enum.reduce(from_y..to_y, paths, & draw.(&2, x, &1, "#"))
      [[from_x, y], [to_x, y]], paths -> Enum.reduce(from_x..to_x, paths, & draw.(&2, &1, y, "#"))
    end)
  end)
  
floor_y = (paths |> Map.values() |> Enum.flat_map(& Map.keys/1) |> Enum.max()) + 2
  
sand_fall = fn 
  paths, {x, y}, _ when y + 1 == floor_y -> 
    draw.(paths, x, y, "o") 
  paths, {x, y}, self ->
    down_y = y + 1
    
    paths
    |> get_in([x, down_y])
    |> case do
      nil -> self.(paths, {x, down_y}, self)
      floor when floor in ["#", "o"] -> 
        cond do
          is_nil(get_in(paths, [x - 1, down_y])) -> self.(paths, {x - 1, down_y}, self)
          is_nil(get_in(paths, [x + 1, down_y])) -> self.(paths, {x + 1, down_y}, self)
          true -> draw.(paths, x, y, "o") 
        end
    end
end
  
Stream.iterate(1, & &1 + 1)
|> Enum.reduce_while(paths, fn unit, paths -> 
  paths
  |> sand_fall.({500, 0}, sand_fall)
  |> case do
    %{500 => %{0 => "o"}} -> {:halt, unit}
    paths -> {:cont, paths}
  end
end)
|> IO.inspect