Packed compact tries: A fast and efficient data structure for online string processing

We present a new data structure called the packed compact trie (packed c-trie) which stores a set S of k strings of total length n in n log + O(k log n) bits of space and supports fast pattern matching queries and updates, where is the alphabet size. Assume that = log n letters are packed in a single machine word on the standard word RAM model, and let f (k; n) denote the query and update times of the dynamic predecessor/successor data structure of our choice which stores k integers from universe [1; n] in O(k log n) bits of space. Then, given a string of length m, our packed c-tries support pattern matching queries and insert/delete operations in O( m f (k; n)) worst-case time and in O( m + f (k; n)) expected time. Our experiments show that our packed c-tries are faster than the standard compact tries (a.k.a. Patricia trees) on real data sets. We also discuss applications of our packed c-tries.