Day 4: Camp Cleanup

Mix.install(
  [
    {:kino_aoc, git: "https://github.com/ljgago/kino_aoc"}
  ],
  force: true
)

Part 1

{:ok, input} = KinoAOC.download_puzzle("2022", "4", System.fetch_env!("LB_WEIZHLIU"))

input_sample = """
2-4,6-8
2-3,4-5
5-7,7-9
2-8,3-7
6-6,4-6
2-6,4-8
"""

defmodule PartOne do
  def has_overlap(pair) do
    pair
    |> String.split(",")
    |> Enum.map(fn pair ->
      pair
      |> String.split("-")
      |> Enum.map(&String.to_integer/1)
    end)
    |> check_overlap?()
  end

  def check_overlap?([[x1, x2], [y1, y2]]) do
    (x1 <= y1 and x2 >= y2) or (x1 >= y1 and x2 <= y2)
  end
end

input
|> String.split("\n", trim: true)
|> Enum.map(&PartOne.has_overlap/1)
|> Enum.count(& &1)

Part 2

input
|> String.split("\n", trim: true)
|> Enum.map(&String.split(&1, ","))
|> Enum.map(
  &(Enum.map(&1, fn p ->
      p
      |> String.split("-")
      |> Enum.map(fn e -> String.to_integer(e) end)
      |> then(fn p -> apply(Range, :new, p) end)
    end)
    |> then(fn [p1, p2] -> Range.disjoint?(p1, p2) end))
)
|> Enum.count(&not/1)

defmodule DayFour do
  def run(input, f) do
    input
    |> String.split("\n", trim: true)
    |> Enum.map(&convert_pair(&1, f))
  end

  def convert_pair(pair, f) do
    pair
    |> String.split(",")
    |> Enum.map(&to_integer_pair(&1, f))
  end

  def to_integer_pair(elf, f) do
    elf
    |> String.split("-")
    |> Enum.map(&String.to_integer/1)
    |> then(f)
  end

  def pair_to_range(pair) do
    apply(Range, :new, pair)
  end

  def check_overlap?([[x1, x2], [y1, y2]]) do
    (x1 <= y1 and x2 >= y2) or (x1 >= y1 and x2 <= y2)
  end
end

part1 =
  DayFour.run(input, & &1)
  |> Enum.map(&DayFour.check_overlap?/1)
  |> Enum.count(& &1)

part2 =
  DayFour.run(input, &DayFour.pair_to_range/1)
  |> Enum.map(&apply(Range, :disjoint?, &1))
  |> Enum.count(&not/1)