Hash tables and 2-3 tree

A prefix trie in which each node that is the only child is merged with its parent. By Claudio Rocchini - Own work, CC BY 2.5, wikimedia result: number of all internal nodes is at most the radix r of the tree, where r=2^{x} \forall x \in \mathbb{R}^d \cap x \ge 1 Edge can be labelled with sequences of elements as well as single elements.