Note that a radix tree and hash table are not mutually exclusive. A radix tree is a way of representing a sparse table. That could be used as a hash table. Ther

Note that a radix tree and hash table are not mutually exclusive. A radix tree is a way of representing a sparse table. That could be used as a hash table. There's a trade off there because if the table is very sparse, and we're using hashing, we could just shrink the table so as not to have it so sparse, and then just make it a regular array. The key aspect of the four corner code is that it mashes together completely unrelated characters. There's no meaningful index to it. It's not easy to look at a four corner code to figure out the list of characters it aliases for.