Advent of code 2024 - day 5

Mix.install([
  {:kino, "~> 0.14.2"}
])

Part 1

https://adventofcode.com/2024/day/5

textarea = Kino.Input.textarea("Give input:")

input = Kino.Input.read(textarea)

[rules, updates] = String.split(input, "\n\n", parts: 2)

rule_set =
  String.split(rules, "\n", trim: true)
  |> Enum.map(fn rule ->
    String.split(rule, "|") |> Enum.map(&String.to_integer/1) |> List.to_tuple()
  end)
  |> Enum.into(MapSet.new())

update_list =
  String.split(updates, "\n", trim: true)
  |> Enum.map(fn update ->
    String.split(update, ",") |> Enum.map(&String.to_integer/1)
  end)

:ok

defmodule PageOrderValidator do
  def wrong_order(rule_set, page_numbers) do
    for idx <- 0..(length(page_numbers) - 2),
        a_page = Enum.at(page_numbers, idx),
        compare_idx <- (idx + 1)..(length(page_numbers) - 1),
        later_page = Enum.at(page_numbers, compare_idx),
        reduce: false do
      acc -> acc || MapSet.member?(rule_set, {later_page, a_page})
    end
  end
end

update_list
|> Enum.filter(fn page_numbers -> !PageOrderValidator.wrong_order(rule_set, page_numbers) end)
|> Enum.map(fn page_numbers ->
  Enum.at(page_numbers, Integer.floor_div(length(page_numbers) - 1, 2))
end)
|> Enum.sum()

Part 2

update_list
|> Enum.filter(fn page_numbers -> PageOrderValidator.wrong_order(rule_set, page_numbers) end)
|> Enum.map(fn page_numbers ->
  Enum.sort(page_numbers, fn left_page, right_page ->
    MapSet.member?(rule_set, {left_page, right_page})
  end)
end)
|> Enum.filter(fn page_numbers ->
  if PageOrderValidator.wrong_order(rule_set, page_numbers) do
    # still wrong, print these
    IO.inspect(page_numbers, charlists: :as_lists)
    false
  else
    true
  end
end)
# |> IO.inspect(charlists: :as_lists)
|> Enum.map(fn page_numbers ->
  Enum.at(page_numbers, Integer.floor_div(length(page_numbers) - 1, 2))
end)
|> Enum.sum()