Advent of Code 2023 Day 9 Part 1

Mix.install([
  {:kino_aoc, "~> 0.1.5"}
])

Get Inputs

{:ok, puzzle_input} =
  KinoAOC.download_puzzle("2023", "9", System.fetch_env!("LB_SESSION"))

My answer

defmodule Resolver do
  def parse(input) do
    input
    |> String.split("\n")
    |> Enum.map(fn line ->
      line
      |> String.split(" ")
      |> Enum.map(&String.to_integer(&1))
    end)
  end

  def resolve(array_list) do
    array_list
    |> Enum.map(fn array ->
      diff_array_list =
        0..(Enum.count(array) - 1)
        |> Enum.reduce_while([array], fn _index, acc ->
          last_array = Enum.at(acc, -1)
          diff_array = diff(last_array)

          if Enum.all?(diff_array, &(&1 == 0)) do
            {:halt, acc ++ [diff_array]}
          else
            {:cont, acc ++ [diff_array]}
          end
        end)

      diff_array_list
      |> Enum.map(fn diff_array ->
        Enum.at(diff_array, -1)
      end)
      |> Enum.sum()
    end)
    |> Enum.sum()
  end

  defp diff(array) do
    {_, a_array} = List.pop_at(array, 0)
    {_, b_array} = List.pop_at(array, -1)

    Enum.zip(a_array, b_array)
    |> Enum.map(fn {a, b} ->
      a - b
    end)
  end
end

array_list =
  """
  0 3 6 9 12 15
  1 3 6 10 15 21
  10 13 16 21 30 45
  """
  |> String.slice(0..-2)
  |> Resolver.parse()

Resolver.resolve(array_list)

array_list = Resolver.parse(puzzle_input)

Resolver.resolve(array_list)