Trie compact representation using double-array structures with string labels

A trie is an ordered tree structure with a character on each edge. The trie provides efficient storing and retrieval of a keyword set in processing strings. The double-array has been proposed to provide fast retrieval in the trie. As its space usage depends on the number of trie nodes, the space usage decreases by reducing nodes. To reduce the number of trie nodes, an Minimal-Prefix (MP) trie and a double-trie have been proposed, and the double-array can represent these data structures efficiently. On the other hand, the data structures include many nodes that can be reduced by giving a string label to each edge. However, the double-array with string labels has not been proposed. This paper proposes a new double-array with string labels by using multiple arrays depending on label sizes. Moreover, we show its effectiveness by experiments.