Top-K Color Queries for Document Retrieval

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Top-K Color Queries for Document Retrieval
In this paper we describe a new efficient (in fact optimal) data structure for the top-K color problem. Each element of an array A is assigned a color c with priority p(c). For a query range [a, b] and a value K, we have to report K colors with the highest priorities among all colors that occur in A[a..b], sorted in reverse order by their priorities. We show that such queries can be answered in O(K) time using an O(N log ) bits data structure, where N is the number of elements in the array and is the number of colors. Thus our data structure is asymptotically optimal with respect to the worst-case query time and space. As an immediate application of our results, we obtain optimal time solutions for several document retrieval problems. The method of the paper could be also of independent interest.
Marek Karpinski, Yakov Nekrich
Added 14 May 2011
Updated 14 May 2011
Type Journal
Year 2010
Where CORR
Authors Marek Karpinski, Yakov Nekrich
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