Stable set and multiset operations in optimal time and space

The focus of this paper is on demonstrating the existence of methods for stably performing set and multiset operations on sorted files of data in both optimal time and optimal extra space. It is already known that stable merging and stable duplicate-key extraction permit such methods. The major new results reported herein are thesean asymptotically optimal time and space algorithm is devised for stably selecting matched records from a sorted file, this selection strategy is employed, along with other algorithmic tools, to prove that all of the elementary binary set operations can be stably performed in optimal time and space on sorted files, and after generalizing these operations to multisets in a natural way for file processing, it is proved that each can be stably performed in optimal time and space on sorted files