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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.
Searching for this string in a database with a trigram-based index would involve finding which objects contain as many of the three trigrams as possible. As a concrete example of using trigram search to search for a regular expression query, consider searching for the string ab[cd]e , where the brackets denote that the third character in the ...
In this example, the indexer is used to get the value at the nth position, and then to get the position in the list referenced by its value. The output of the code is: John is the member number 0 of the doeFamily Jane is the member number 1 of the doeFamily
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 ...
The length of a string can also be stored explicitly, for example by prefixing the string with the length as a byte value. This convention is used in many Pascal dialects; as a consequence, some people call such a string a Pascal string or P-string. Storing the string length as byte limits the maximum string length to 255.
A string-searching algorithm, sometimes called string-matching algorithm, is an algorithm that searches a body of text for portions that match by pattern. A basic example of string searching is when the pattern and the searched text are arrays of elements of an alphabet ( finite set ) Σ.
(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 ...
String kernel; Substring index; U. Ukkonen's algorithm; W. Wagner–Fischer algorithm This page was last edited on 29 August 2020, at 17:30 (UTC). Text is available ...