aoc2021-day 5

Part 1

Mix.install([{:kino, "~> 0.4.0"}])

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

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  String.split(line, [",", " -> "], trim: true) |> Enum.map(&String.to_integer/1)
end)
|> Enum.reduce(%{}, fn
  [ax, ay, ax, by], acc ->
    for y <- ay..by, reduce: acc do
      map -> Map.update(map, {ax, y}, 1, &amp;(&amp;1 + 1))
    end

  [ax, ay, bx, ay], acc ->
    for x <- ax..bx, reduce: acc do
      map -> Map.update(map, {x, ay}, 1, &amp;(&amp;1 + 1))
    end

  # only consider horizontal and vertical lines
  _other, acc ->
    acc
end)
|> Enum.count(fn {{_x, _y}, c} -> c >= 2 end)

Part 2

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  String.split(line, [",", " -> "], trim: true) |> Enum.map(&String.to_integer/1)
end)
|> Enum.reduce(%{}, fn
  [ax, ay, ax, by], acc ->
    for y <- ay..by, reduce: acc do
      map -> Map.update(map, {ax, y}, 1, &amp;(&amp;1 + 1))
    end

  [ax, ay, bx, ay], acc ->
    for x <- ax..bx, reduce: acc do
      map -> Map.update(map, {x, ay}, 1, &amp;(&amp;1 + 1))
    end

  [ax, ay, bx, by], acc when abs(ax - bx) == abs(ay - by) ->
    for {x, y} <- Enum.zip(ax..bx, ay..by), reduce: acc do
      map -> Map.update(map, {x, y}, 1, &amp;(&amp;1 + 1))
    end

  _other, acc ->
    acc
end)
|> Enum.count(fn {{_x, _y}, c} -> c >= 2 end)

Mix.install([{:ecto, "~> 3.7"}])

defmodule Test do
  def test() do
    "Hello World"
  end
end

Test.test()