An efficient method of compressing binary tries

Abstract

In many applications, information retrieval is a very important research field. In several key strategies, the binary trie is famous as a fast access method to be able to retrieve keys in order. However, if the binary trie is implemented, the greater the number of the registered keys, the larger storage in secondary memory is required. In order to solve this problem, Jonge et al. (1987) proposed the method to change the binary trie into a compact bit stream (called the pre-order bit stream). However, searching and updating a key takes a lot of time in large key sets. This paper proposes an efficient binary digital search algorithm by introducing a new hierarchical structure. The algorithms for retrieval, insertion and deletion of keys using this new method are introduced through examples. The theoretical and experimental results, using 50,000 Japanese nouns and 50,000 English words, show that this method provides faster access than the traditional method. Retrieval is 18/spl sim/20 times, the insertion is 11/spl sim/13 times and the deletion is 4/spl sim/6 times faster.