Day 5

Mix.install([
  {:kino, "~> 0.6.2"}
])

Input

input = Kino.Input.textarea("Paster your inputr")

board = %{}

sample = """
0,9 -> 5,9
8,0 -> 0,8
9,4 -> 3,4
2,2 -> 2,1
7,0 -> 7,4
6,4 -> 2,0
0,9 -> 2,9
3,4 -> 1,4
0,0 -> 8,8
5,5 -> 8,2
"""

Part 1

board =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(fn line ->
    String.split(line, [",", " -> "]) |> Enum.map(&String.to_integer/1) |> List.to_tuple()
  end)
  |> Enum.reduce(%{}, fn
    {x, y1, x, y2}, board ->
      Enum.reduce(y1..y2, board, fn y, b -> Map.update(b, {x, y}, 1, &(&1 + 1)) end)

    {x1, y, x2, y}, board ->
      Enum.reduce(x1..x2, board, fn x, b -> Map.update(b, {x, y}, 1, &(&1 + 1)) end)

    _, board ->
      board
  end)

Map.values(board) |> Enum.count(&(&1 >= 2))

Part 2

board =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(fn line ->
    String.split(line, [",", " -> "]) |> Enum.map(&String.to_integer/1) |> List.to_tuple()
  end)
  |> Enum.reduce(%{}, fn
    {x, y1, x, y2}, board ->
      Enum.reduce(y1..y2, board, fn y, b -> Map.update(b, {x, y}, 1, &(&1 + 1)) end)

    {x1, y, x2, y}, board ->
      Enum.reduce(x1..x2, board, fn x, b -> Map.update(b, {x, y}, 1, &(&1 + 1)) end)

    {x1, y1, x2, y2}, board ->
      s = Integer.floor_div(y2 - y1, x2 - x1)
      # IO.inspect("#{i} -> #{x1 + i} , #{x2 + s * i} <- #{x1} #{x2} #{y1} #{y2}") 
      Enum.reduce(0..(x2 - x1), board, fn i, b ->
        Map.update(b, {x1 + i, y1 + s * i}, 1, &amp;(&amp;1 + 1))
      end)
  end)

Map.values(board) |> Enum.count(&(&1 >= 2))