Day 03

Mix.install([:kino_aoc])

Section

{:ok, puzzle_input} =
  KinoAOC.download_puzzle("2025", "3", System.fetch_env!("LB_ADVENT_OF_CODE_SESSION"))

batteries =
  puzzle_input
  |> String.split("\n", trim: true)
  |> Enum.map(fn row ->
    row
    |> String.to_charlist()
    |> Enum.map(& &1 - ?0)
  end)

defmodule Joltage do
  def make_largest(list, n) do
    to_remove = length(list) - n
    Enum.reduce(1..to_remove, list, fn _, acc -> make_larger(acc) end)
  end
  
  def make_larger([_]), do: []
  def make_larger([a, b | rest]) when a < b, do: [b | rest]
  def make_larger([b | rest]), do: [b | make_larger(rest)]
end

Part 1

Enum.sum_by(batteries, &Integer.undigits(Joltage.make_largest(&1, 2)))

Part 2

Enum.sum_by(batteries, &Integer.undigits(Joltage.make_largest(&1, 12)))