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A new approach is proposed for the design of perfect hash functions. The algorithms developed can be effectively applied to key sets of large size. The basic ideas employed in the construction are rehash and segmentation. Analytic results are given which are applicable when problem sizes are small. Extensive experiments have been performed to test the(More)
The LCS problem is to determine a longest common subsequence (LCS) of two symbol sequences. Two algorithms which improve two existing results, respectively, are presented. Let m, n be the lengths of the two input strings, with m Q n, p being the length of the LCS, and s being the number of distinct symbols appearing in the two strings. It is shown that the(More)
In this paper, we shall show that the symbolic Gray code hashing mechanism is not only good for best matching, but also good for partial match queries. Essentially, we shall propose a new hashing scheme, called bucket-oriented symbolic Gray code, which can be used to produce any arbitrary Cartesian product file, which has been shown to be good for partial(More)
In this paper, we shall derive two formulas for the average number of buckets to be examined over all possible partial match queries for Cartesian product files and random files, respectively. The superiority of the Cartesian product file is established. A new multi-key file, called a partition file, is introduced. It is shown that both Cartesian product(More)
This paper presents a new dynamic file organization scheme based on hashing. The hash functions used here, being defined by extended hash indicator tables (EHITs), are both dynamic and perfect. The allocated storage space can be enlarged and shrunk without reorganizing the data file. Simulation results show'that the storage utilization is approximately(More)