An elastic-degenerate string is a sequence of n sets of strings of total length N. It has been introduced to represent multiple sequence alignments of closely-related sequences in a compact form. For a standard pattern of length m, pattern matching in an elastic-degenerate text can be solved on-line in time O(nm^2+N) with pre-processing time and space O(m) (Grossi et al., CPM 2017). A fast bit-vector algorithm requiring time O(N * ceil[m/w]) with pre-processing time and space O(m * ceil[m/w]), where w is the size of the computer word, was also presented. In this paper we consider the same problem for a set of patterns of total length M. A straightforward generalization of the existing bit-vector algorithm would require time O(N * ceil[M/w]) with pre-processing time and space O(M * ceil[M/w]), which is prohibitive in practice. We present a new on-line O(N * ceil[M/w])-time algorithm with pre-processing time and space O(M). We present experimental results using both synthetic and real data demonstrating the performance of the algorithm. We further demonstrate a real application of our algorithm in a pipeline for discovery and verification of minimal absent words (MAWs) in the human genome showing that a significant number of previously discovered MAWs are in fact false-positives when a population's variants are considered.
@InProceedings{pissis_et_al:LIPIcs.SEA.2018.16, author = {Pissis, Solon P. and Retha, Ahmad}, title = {{Dictionary Matching in Elastic-Degenerate Texts with Applications in Searching VCF Files On-line}}, booktitle = {17th International Symposium on Experimental Algorithms (SEA 2018)}, pages = {16:1--16:14}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-070-5}, ISSN = {1868-8969}, year = {2018}, volume = {103}, editor = {D'Angelo, Gianlorenzo}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SEA.2018.16}, URN = {urn:nbn:de:0030-drops-89515}, doi = {10.4230/LIPIcs.SEA.2018.16}, annote = {Keywords: on-line algorithms, algorithms on strings, dictionary matching, elastic-degenerate string, Variant Call Format} }
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