day16.rb

if ARGV.empty?
  data = DATA.readlines(chomp: true)
else
  data = File.readlines(ARGV[0], chomp: true)
end

VALVES = {}
GRAPH = {}

data.each do |line|
  match = /Valve (?<name>[A-Z]{2}) has flow rate=(?<rate>\d+); tunnels? leads? to valves? (?<valves>.*)/.match(line)
  VALVES[match[:name]] = match[:rate].to_i
  GRAPH[match[:name]] = match[:valves].split(', ')
end

p VALVES
p GRAPH

$cache = {}
def max_flow(current, opened, time)
  return 0 if time <= 0
  key = [current, opened, time]
  return $cache[key] if $cache.key?(key)

  max = 0
  # If we open the current valve
  if !opened.include?(current)
    current_opened = opened + [current]
    pressure = VALVES[current] * (time - 1)
    if pressure != 0
      current_max = pressure + max_flow(current, current_opened.sort, time - 1)
      max = current_max if current_max > max
    end
  end

  GRAPH[current].each do |next_valve|
    current_max = max_flow(next_valve, opened, time - 1)
    max = current_max if current_max > max
  end

  $cache[key] = max
  max
end

p max_flow("AA", [], 30)


__END__
Valve AA has flow rate=0; tunnels lead to valves DD, II, BB
Valve BB has flow rate=13; tunnels lead to valves CC, AA
Valve CC has flow rate=2; tunnels lead to valves DD, BB
Valve DD has flow rate=20; tunnels lead to valves CC, AA, EE
Valve EE has flow rate=3; tunnels lead to valves FF, DD
Valve FF has flow rate=0; tunnels lead to valves EE, GG
Valve GG has flow rate=0; tunnels lead to valves FF, HH
Valve HH has flow rate=22; tunnel leads to valve GG
Valve II has flow rate=0; tunnels lead to valves AA, JJ
Valve JJ has flow rate=21; tunnel leads to valve II

https://youtu.be/LzDRS7igO1k