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A bitmap index is a special kind of indexing that stores the bulk of its data as bit arrays (bitmaps) and answers most queries by performing bitwise logical operations on these bitmaps. The most commonly used indexes, such as B+ trees, are most efficient if the values they index do not repeat or repeat a small number of times. In contrast, the ...
For a trivial hash function lookup, the unsigned raw data value is used directly as an index to a one-dimensional table to extract a result. For small ranges, this can be amongst the fastest lookup, even exceeding binary search speed with zero branches and executing in constant time .
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.
This lookup will return the occurrence of c in P with the next-highest index < or -1 if there is no such occurrence. The proposed shift will then be i − j {\displaystyle i-j} , with O ( 1 ) {\displaystyle O(1)} lookup time and O ( k m ) {\displaystyle O(km)} space, assuming a finite alphabet of length k .
Given a list L of n elements with values or records L 0.... L n−1, and target value T, the following subroutine uses linear search to find the index of the target T in L. [3] Set i to 0. If L i = T, the search terminates successfully; return i. Increase i by 1. If i < n, go to step 2. Otherwise, the search terminates unsuccessfully.
In computer science, an algorithm for matching wildcards (also known as globbing) is useful in comparing text strings that may contain wildcard syntax. [1] Common uses of these algorithms include command-line interfaces, e.g. the Bourne shell [2] or Microsoft Windows command-line [3] or text editor or file manager, as well as the interfaces for some search engines [4] and databases. [5]
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A hash table uses a hash function to compute an index, also called a hash code, into an array of buckets or slots, from which the desired value can be found. During lookup, the key is hashed and the resulting hash indicates where the corresponding value is stored. A map implemented by a hash table is called a hash map.