Day 5: Hydrothermal Venture

Mix.install([:kino])

input = Kino.Input.textarea("Please paste your input:")

Setup

inputs =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(fn input ->
    input
    |> String.split(" -> ", trim: true)
    |> Enum.map(fn point ->
      point |> String.split(",") |> Enum.map(&String.to_integer/1)
    end)
  end)

Part 1

https://adventofcode.com/2021/day/5

Solve: Part 1

inputs
|> Enum.reduce(%{}, fn input, point_count_map ->
  new_points =
    case input do
      [[x, y1], [x, y2]] -> y1..y2 |> Enum.map(&[x, &1])
      [[x1, y], [x2, y]] -> x1..x2 |> Enum.map(&[&1, y])
      _ -> []
    end

  new_points
  |> Enum.reduce(point_count_map, fn point, point_count_map ->
    point_count_map |> Map.update(point, 1, &(&1 + 1))
  end)
end)
|> Enum.count(fn {_key, value} -> value >= 2 end)

Part 2

https://adventofcode.com/2021/day/5#part2

Solve: Part 2

inputs
|> Enum.reduce(%{}, fn input, point_count_map ->
  new_points =
    case input do
      [[x, y1], [x, y2]] -> y1..y2 |> Enum.map(&[x, &1])
      [[x1, y], [x2, y]] -> x1..x2 |> Enum.map(&[&1, y])
      [[x1, y1], [x2, y2]] -> Enum.zip_with(x1..x2, y1..y2, &[&1, &2])
    end

  new_points
  |> Enum.reduce(point_count_map, fn point, point_count_map ->
    point_count_map |> Map.update(point, 1, &(&1 + 1))
  end)
end)
|> Enum.count(fn {_key, value} -> value >= 2 end)