A quadtree, where every node is first looked up in a hash table before simulating it. Eventually the hash table has enough entries to where most changes aren't

A quadtree, where every node is first looked up in a hash table before simulating it. Eventually the hash table has enough entries to where most changes aren't even simulated but just looked up. It's a pretty plain CPU/memory tradeoff, but it works surprisingly well for game of life.