Simple compression code supporting random access and fast string matching

Abstract

Given a sequence S of n symbols over some alphabet ∑, we develop a new compression method that is (i) very simple to implement; (ii) provides O(1) time random access to any symbol of the original sequence; (iii) allows efficient pattern matching over the compressed sequence. Our simplest solution uses at most 2h + o(h) bits of space, where h = n(H0(S) + 1), and H 0(S) is the zeroth-order empirical entropy of S. We discuss a number of improvements and trade-offs over the basic method. The new method is applied to text compression. We also propose average case optimal string matching algorithms. © Springer-Verlag Berlin Heidelberg 2007.