Computing Inverse ST in Linear Complexity

  • Authors:
  • Ge Nong;Sen Zhang;Wai Hong Chan

  • Affiliations:
  • Computer Science Department, Sun Yat-Sen University, P.R.C.;Dept. of Math., Comp. Sci. and Stat., SUNY College at Oneonta, U.S.A.;Department of Mathematics, Hong Kong Baptist University, Hong Kong

  • Venue:
  • CPM '08 Proceedings of the 19th annual symposium on Combinatorial Pattern Matching
  • Year:
  • 2008

Quantified Score

Hi-index 0.00

Visualization

Abstract

The Sort Transform (ST) can significantly speed up the block sorting phase of the Burrows-Wheeler transform (BWT) by sorting only limited order contexts. However, the best result obtained so far for the inverse ST has a time complexity O(Nlogk) and a space complexity O(N), where Nand kare the text size and the context order of the transform, respectively. In this paper, we present a novel algorithm that can compute the inverse ST in an O(N) time/space complexity, a linear result independent of k. The main idea behind the design of the linear algorithm is a set of cycle properties of k-order contexts we explored for this work. These newly discovered cycle properties allow us to quickly compute the longest common prefix (LCP) between any pair of adjacent k-order contexts that may belong to two different cycles, leading to the proposed linear inverse ST algorithm.