AOC 2023 - Day 6

Mix.install([
  {:kino_aoc, "~> 0.1"}
])

Input

{:ok, puzzle_input} =
  KinoAOC.download_puzzle("2023", "6", System.fetch_env!("LB_AOC_SESSION"))

Code

data =
  puzzle_input
  |> String.split("\n")
  |> Enum.map(fn str ->
    str
    |> String.split()
    |> Enum.drop(1)
    |> Enum.map(&String.to_integer/1)
  end)
  |> Enum.zip()

Part 1

new_records =
  Enum.map(data, fn {time, record} ->
    1..(time - 1)
    |> Enum.reduce([], fn time_to_hold, acc ->
      remaining_time = time - time_to_hold
      length = time_to_hold * remaining_time

      if length > record do
        [length | acc]
      else
        acc
      end
    end)
  end)

ways_to_beat =
  new_records
  |> Enum.map(&Enum.count/1)

Enum.reduce(ways_to_beat, nil, fn num, acc ->
  if acc do
    acc * num
  else
    num
  end
end)

Part 2

[time, record] =
  puzzle_input
  |> String.split("\n")
  |> Enum.map(fn str ->
    str
    |> String.split()
    |> Enum.drop(1)
    |> Enum.join()
    |> String.to_integer()
  end)

Enum.reduce(1..(time - 1), 0, fn time_to_hold, acc ->
  remaining_time = time - time_to_hold
  length = time_to_hold * remaining_time
  if length > record, do: acc + 1, else: acc
end)