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find(string,substring) returns integer Description Returns the position of the start of the first occurrence of substring in string. If the substring is not found most of these routines return an invalid index value – -1 where indexes are 0-based, 0 where they are 1-based – or some value to be interpreted as Boolean FALSE. Related instrrev
The de Bruijn sequence for alphabet size k = 2 and substring length n = 2. In general there are many sequences for a particular n and k but in this example it is unique, up to cycling. In combinatorial mathematics , a de Bruijn sequence of order n on a size- k alphabet A is a cyclic sequence in which every possible length- n string on A occurs ...
A string is a substring (or factor) [1] of a string if there exists two strings and such that =.In particular, the empty string is a substring of every string. Example: The string = ana is equal to substrings (and subsequences) of = banana at two different offsets:
Algebraic laws for regular expressions can be obtained using a method by Gischer which is best explained along an example: In order to check whether (X+Y) * and (X * Y *) * denote the same regular language, for all regular expressions X, Y, it is necessary and sufficient to check whether the particular regular expressions (a+b) * and (a * b ...
Given two different words of the same length, say a = a 1 a 2...a k and b = b 1 b 2...b k, the order of the two words depends on the alphabetic order of the symbols in the first place i where the two words differ (counting from the beginning of the words): a < b if and only if a i < b i in the underlying order of the alphabet A.
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.
The longest common substrings of a set of strings can be found by building a generalized suffix tree for the strings, and then finding the deepest internal nodes which have leaf nodes from all the strings in the subtree below it. The figure on the right is the suffix tree for the strings "ABAB", "BABA" and "ABBA", padded with unique string ...
The total length of all the strings on all of the edges in the tree is (), but each edge can be stored as the position and length of a substring of S, giving a total space usage of () computer words. The worst-case space usage of a suffix tree is seen with a fibonacci word , giving the full 2 n {\displaystyle 2n} nodes.