day_16.livemd

Day 16

Mix.install([:kino])

Section

input = Kino.Input.textarea("Put your data here")

input =
  input
  |> Kino.Input.read()
  |> String.split("\n")
  |> Enum.map(fn line ->
    [_, valve, rate, to] =
      ~r/Valve ([A-Z]{2}) has flow rate=(\d*); (?:tunnels|tunnel) (?:lead|leads) to (?:valves|valve) (.*)/
      |> Regex.run(line)

    {valve, String.to_integer(rate), String.split(to, ", ")}
  end)
  |> Enum.reduce(%{}, fn {valve, rate, to}, map -> Map.put(map, valve, {rate, to}) end)

defmodule Day16 do

  def create(_valves, states, minute) when minute == 30 do
    states
  end

  def create(valves, states, minute) do
    create(valves, states, [], minute)
  end

  def create(valves, {{pos_1, pos_2}, open, cur_rate, acc_rate} | tl], new_states, minute) do
    {rate, to} = Map.get(valves, valve)
    is_open = Map.has_key?(open, valve)

    updated_states = Enum.reduce(to, [], fn to, list ->
      [{to, open, cur_rate, acc_rate + cur_rate} | list]
    end)
    
    updated_states = if is_open do
      updated_states
    else
      [{valve, Map.put(open, valve, nil), cur_rate + rate, acc_rate + cur_rate} | updated_states]
    end
    
    create(valves, tl, updated_states ++ new_states, minute)
  end

  def create(valves, [], new_states, minute) do
    # We take the fittest
    new_states = new_states
    |> Enum.sort(fn {_,_,_,p1},{_,_,_,p2} -> p1 > p2 end)
    |> Enum.take(1000)
    create(valves, new_states, minute + 1)
  end

end

Part 1

init_state = [{"AA", %{}, 0, 0}]

Day16.create(input, init_state, 0)
|> Enum.max(fn {_, _, _, p1}, {_, _, _, p2} -> p1 > p2 end)

Part 2

dim = 4_000_000

{x, y} =
  input
  |> Day15.add_distances()
  |> Day15.find_beacon({0, 0}, dim)

x * dim + y