Streaming $k$-edit approximate pattern matching via string decomposition

Abstract: In this paper we give an algorithm for streaming $k$-edit approximate pattern matching which uses space $\widetilde{O}(k<sup>2)$ and time $\widetilde{O}(k<sup>2)$ per arriving symbol. This improves substantially on the recent algorithm of Kociumaka, Porat and Starikovskaya (2022) which uses space $\widetilde{O}(k<sup>5)$ and time $\widetilde{O}(k<sup>8)$ per arriving symbol. In the $k$-edit approximate pattern matching problem we get a pattern $P$ and text $T$ and we want to identify all substrings of the text $T$ that are at edit distance at most $k$ from $P$. In the streaming version of this problem both the pattern and the text arrive in a streaming fashion symbol by symbol and after each symbol of the text we need to report whether there is a current suffix of the text with edit distance at most $k$ from $P$. We measure the total space needed by the algorithm and time needed per arriving symbol.