Advent of code day 04

Mix.install([
  {:kino, "~> 0.5.0"}
])

Setup input

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

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

Part 01

defmodule Helper do
  def xmas?({x, y} = point, grid) do
    down =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x, y + 1}, ".") <>
        Map.get(grid, {x, y + 2}, ".") <>
        Map.get(grid, {x, y + 3}, ".")

    up =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x, y - 1}, ".") <>
        Map.get(grid, {x, y - 2}, ".") <>
        Map.get(grid, {x, y - 3}, ".")

    backwards =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x - 1, y}, ".") <>
        Map.get(grid, {x - 2, y}, ".") <>
        Map.get(grid, {x - 3, y}, ".")

    horizontal =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x + 1, y}, ".") <>
        Map.get(grid, {x + 2, y}, ".") <>
        Map.get(grid, {x + 3, y}, ".")

    dig_down_left =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x - 1, y + 1}, ".") <>
        Map.get(grid, {x - 2, y + 2}, ".") <>
        Map.get(grid, {x - 3, y + 3}, ".")

    dig_up_left =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x + 1, y - 1}, ".") <>
        Map.get(grid, {x + 2, y - 2}, ".") <>
        Map.get(grid, {x + 3, y - 3}, ".")

    dig_down_right =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x + 1, y + 1}, ".") <>
        Map.get(grid, {x + 2, y + 2}, ".") <>
        Map.get(grid, {x + 3, y + 3}, ".")

    dig_up_right =
      Map.get(grid, point, ".") <>
        Map.get(grid, {x - 1, y - 1}, ".") <>
        Map.get(grid, {x - 2, y - 2}, ".") <>
        Map.get(grid, {x - 3, y - 3}, ".")

    [up, down, horizontal, backwards, dig_down_left, dig_down_right, dig_up_left, dig_up_right]
    |> Enum.filter(fn e -> e == "XMAS" end)
    |> Enum.count()
  end
end

parsed =
  example
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.map(&(String.split(&1, "", trim: true) |> List.to_tuple()))
  |> List.to_tuple()

lines = tuple_size(parsed) - 1
cols = tuple_size(elem(parsed, 0)) - 1

grid =
  for l <- 0..lines, c <- 0..cols, into: %{} do
    {{l, c}, elem(elem(parsed, l), c)}
  end

Enum.reduce(grid, 0, fn {key, v}, acc ->
  if v == "X" do
    acc + Helper.xmas?(key, grid)
  else
    acc
  end
end)

Part 02

defmodule Helper2 do
  def mas?({x, y} = point, grid) do
    left_dig =
      Map.get(grid, {x - 1, y - 1}, ".") <>
        Map.get(grid, point, ".") <>
        Map.get(grid, {x + 1, y + 1}, ".")

    right_dig =
      Map.get(grid, {x - 1, y + 1}, ".") <>
        Map.get(grid, point, ".") <>
        Map.get(grid, {x + 1, y - 1}, ".")

    if right_dig in ["SAM", "MAS"] and left_dig in ["SAM", "MAS"] do
      1
    else
      0
    end
  end
end

Enum.reduce(grid, 0, fn {key, v}, acc ->
  if v == "A" do
    acc + Helper2.mas?(key, grid)
  else
    acc
  end
end)