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rfind(string,substring) returns integer Description Returns the position of the start of the last 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 instr
In informal terms, this algorithm considers every possible substring of the input string and sets [,,] to be true if the substring of length starting from can be generated from the nonterminal . Once it has considered substrings of length 1, it goes on to substrings of length 2, and so on.
A brute-force approach would be to compute the edit distance to P for all substrings of T, and then choose the substring with the minimum distance. However, this algorithm would have the running time O(n 3 m). A better solution, which was proposed by Sellers, [2] relies on dynamic programming.
Let be a regular language. Then there exists an integer depending only on such that every string in of length at least (is called the "pumping length") [4] can be written as = (i.e., can be divided into three substrings), satisfying the following conditions:
The split point is at the end of a string (i.e. after the last character of a leaf node) The split point is in the middle of a string. The second case reduces to the first by splitting the string at the split point to create two new leaf nodes, then creating a new node that is the parent of the two component strings.
Ukkonen's 1985 algorithm takes a string p, called the pattern, and a constant k; it then builds a deterministic finite state automaton that finds, in an arbitrary string s, a substring whose edit distance to p is at most k [13] (cf. the Aho–Corasick algorithm, which similarly constructs an automaton to search for any of a number of patterns ...
Longest common substring problem: find the longest string (or strings) that is a substring (or are substrings) of two or more strings; Substring search. Aho–Corasick string matching algorithm: trie based algorithm for finding all substring matches to any of a finite set of strings
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.