A new heuristic for full trie minimization

Abstract

Trie is a data structure with many applications. High space usage is the major drawback of the trie. The order-containing trie optimizes the space usage of the trie by rearranging symbols of strings. We present a new heuristic for building order-containing tries with small space. The heuristic is based on the following observation. For a given string set P, by moving the symbols on a position to the first position of strings in P, the trie of the resulting pattern set may have fewer nodes than that of the trie of P. We present an algorithm to find positions that yield the smallest such trie. The algorithm runs in O(P) time and uses O(|P| log|P|) bits space, where P is the number of total symbols in P, and |P| is the number of patterns in P. By using this method recursively in trie constructions, we can build a trie with fewer nodes than the trie of P. We conduct several experiments that show the new heuristic builds smaller tires than previous work.