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In computer science, a substring index is a data structure which gives substring search in a text or text collection in sublinear time. Once constructed from a document or set of documents, a substring index can be used to locate all occurrences of a pattern in time linear or near-linear in the pattern size, with no dependence or only logarithmic dependence on the document size.
A simple and inefficient way to see where one string occurs inside another is to check at each index, one by one. First, we see if there is a copy of the needle starting at the first character of the haystack; if not, we look to see if there's a copy of the needle starting at the second character of the haystack, and so forth.
(char-index char string) ISLISP: returns nil: List.elemIndex char string: Haskell (returns Just index) returns Nothing: String.index string char: OCaml: raises Not_found: position = SCAN (string, set «, back» «, kind») position = VERIFY (string, set «, back» «, kind») Fortran: returns zero string indexOf: char ifAbsent: aBlock string ...
First-argument indexing is the most common strategy where the first argument is used as index. It distinguishes atomic values and the principal functor of compound terms. Nonfirst argument indexing is a variation of first-argument indexing that uses the same or similar techniques as first-argument indexing on one or more alternative arguments.
In computer science, an FM-index is a compressed full-text substring index based on the Burrows–Wheeler transform, with some similarities to the suffix array.It was created by Paolo Ferragina and Giovanni Manzini, [1] who describe it as an opportunistic data structure as it allows compression of the input text while still permitting fast substring queries.
Word2vec is a group of related models that are used to produce word embeddings.These models are shallow, two-layer neural networks that are trained to reconstruct linguistic contexts of words.
Techniques such as alphabet reduction may alleviate the high space complexity by reinterpreting the original string as a long string over a smaller alphabet i.e. a string of n bytes can alternatively be regarded as a string of 2n four-bit units and stored in a trie with sixteen pointers per node. However, lookups need to visit twice as many ...
Venn diagram showing the union of sets A and B as everything not in white. In combinatorics, the inclusion–exclusion principle is a counting technique which generalizes the familiar method of obtaining the number of elements in the union of two finite sets; symbolically expressed as