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Showing papers on "Approximate string matching published in 1987"


Journal ArticleDOI
TL;DR: This approach allows an efficient and natural way to construct iconic indexes for pictures and proves the necessary and sufficient conditions to characterize ambiguous pictures for reduced 2D strings as well as normal 2-D strings.
Abstract: In this paper, we describe a new way of representing a symbolic picture by a two-dimensional string. A picture query can also be specified as a 2-D string. The problem of pictorial information retrieval then becomes a problem of 2-D subsequence matching. We present algorithms for encoding a symbolic picture into its 2-D string representation, reconstructing a picture from its 2-D string representation, and matching a 2-D string with another 2-D string. We also prove the necessary and sufficient conditions to characterize ambiguous pictures for reduced 2-D strings as well as normal 2-D strings. This approach thus allows an efficient and natural way to construct iconic indexes for pictures.

674 citations


Journal ArticleDOI
TL;DR: A generalization of string matching, in which the pattern is a sequence of pattern elements, each compatible with a set of symbols, is investigated, which shows that generalized string matching requires a time-space product of $\Omega ({{n^2 } / {\log n}})$ on a powerful model of computation, when the alphabet is restricted to n symbols.
Abstract: Given a pattern string of length n and an object string of length m, the string matching problem asks for the positions of all occurrences of the pattern in the object string. This paper investigates a generalization of string matching, in which the pattern is a sequence of pattern elements, each compatible with a set of symbols. The alphabet of symbols is infinite, with its members encoded in a finite alphabet. In contrast to standard string matching, which can be solved in simultaneous linear time and constant space, it is shown that generalized string matching requires a time-space product of $\Omega ({{n^2 } / {\log n}})$ on a powerful model of computation, when the alphabet is restricted to n symbols. Our proof uses a method of Borodin. The obvious algorithm for generalized string matching requires time $O(NM)$, where N is the length of the encoding of the pattern, and M is that of the object string. We describe an algorithm which solves generalized string matching in time $O(N + M + mN^{{1 / 2}} {\o...

351 citations


Journal ArticleDOI
TL;DR: Two improved algorithms for string matching with k mismatches are presented, one based on fast integer multiplication algorithms whereas the other follows more closely classic string-matching techniques.

28 citations