منابع مشابه
Universal Hashing and Perfect Hashing
Each of the key values x comes from a universe U , i.e. x ∈ U . In this document, we assume U = {1, 2, . . . N}. Observe that the set S is a dynamic set. Each of the Insert and Delete operations may modify the set. Hence the size of the set S changes with each operation. We bound the maximum size of the set to n (n << N). What are the data structures that can be used to store the set S? One opt...
متن کاملPerfect Consistent Hashing
Consistent Hashing functions are widely used for load balancing across a variety of applications. However, the original presentation and typical implementations of Consistent Hashing rely on randomised allocation of hash codes to keys which results in a flawed and approximately-uniform allocation of keys to hash codes. We analyse the desired properties and present an algorithm that perfectly ac...
متن کاملPractical Perfect Hashing
A practical method is presented that permits retrieval from a table in constant time. The method is suitable for large tables and consumes, in practice, O(n) space for n table elements. In addition, the table and the hashing function can be constructed in O(n) expected time. Variations of the method that offer different compromises between storage usage and update time are presented.
متن کاملQuasi-Perfect Hashing
The idea of quasi-perfect hashing is introduced and applied to solve the static dictionary problem. Given a universe U and a set S of n distinct keys belonging to U , we propose a quasi-perfect hash function which allows one to find a key from S, stored in the hash table of size m, m ≥ n, in O(1) time. While looking up a key at most two probes in the hash table are made. Our main motivation is ...
متن کاملPerfect Hashing and Probability
A simple proof is given of the best known upper bound on the cardinality of a set of vectors of length t over an alphabet of size b, with the property that, for every subset of k vectors there is a coordinate in which they all differ. This question is motivated by the study of perfect hash functions. A set of vectors of length t over an alphabet of size b is called k-separated if for every k di...
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 1997
ISSN: 0304-3975
DOI: 10.1016/s0304-3975(96)00146-6