Results 11  20
of
65
Dynamic Ordered Sets with Exponential Search Trees
 Combination of results presented in FOCS 1996, STOC 2000 and SODA
, 2001
"... We introduce exponential search trees as a novel technique for converting static polynomial space search structures for ordered sets into fullydynamic linear space data structures. This leads to an optimal bound of O ( √ log n/log log n) for searching and updating a dynamic set of n integer keys i ..."
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Cited by 26 (1 self)
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We introduce exponential search trees as a novel technique for converting static polynomial space search structures for ordered sets into fullydynamic linear space data structures. This leads to an optimal bound of O ( √ log n/log log n) for searching and updating a dynamic set of n integer keys in linear space. Here searching an integer y means finding the maximum key in the set which is smaller than or equal to y. This problem is equivalent to the standard text book problem of maintaining an ordered set (see, e.g., Cormen, Leiserson, Rivest, and Stein: Introduction to Algorithms, 2nd ed., MIT Press, 2001). The best previous deterministic linear space bound was O(log n/log log n) due Fredman and Willard from STOC 1990. No better deterministic search bound was known using polynomial space.
Two and ThreeDimensional Point Location in Rectangular Subdivisions
 Journal of Algorithms
, 1995
"... We apply van Emde Boastype stratified trees to point location problems in rectangular subdivisions in 2 and 3 dimensions. In a subdivision with n rectangles having integer coordinates from [0; U \Gamma 1], we locate an integer query point in O((log log U ) d ) query time using O(n) space when d ..."
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Cited by 20 (1 self)
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We apply van Emde Boastype stratified trees to point location problems in rectangular subdivisions in 2 and 3 dimensions. In a subdivision with n rectangles having integer coordinates from [0; U \Gamma 1], we locate an integer query point in O((log log U ) d ) query time using O(n) space when d 2 or O(n log log U ) space when d = 3. Applications and extensions of this "fixed universe" approach include spatial point location using logarithmic time and linear space in rectilinear subdivisions having arbitrary coordinates, point location in coriented polygons or fat triangles in the plane, point location in subdivisions of space into "fat prisms," and vertical ray shooting among horizontal "fat objects." Like other results on stratified trees, our algorithms run on a RAM model and make use of perfect hashing. 1 Introduction The point location problemwhich seeks to preprocess a set of disjoint geometric objects to be able to determine quickly which object contains a query point...
Monotone Minimal Perfect Hashing: Searching a Sorted Table with O(1) Accesses
"... A minimal perfect hash function maps a set S of n keys into the set { 0, 1,..., n − 1} bijectively. Classical results state that minimal perfect hashing is possible in constant time using a structure occupying space close to the lower bound of log e bits per element. Here we consider the problem of ..."
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Cited by 20 (8 self)
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A minimal perfect hash function maps a set S of n keys into the set { 0, 1,..., n − 1} bijectively. Classical results state that minimal perfect hashing is possible in constant time using a structure occupying space close to the lower bound of log e bits per element. Here we consider the problem of monotone minimal perfect hashing, in which the bijection is required to preserve the lexicographical ordering of the keys. A monotone minimal perfect hash function can be seen as a very weak form of index that provides ranking just on the set S (and answers randomly outside of S). Our goal is to minimise the description size of the hash function: we show that, for a set S of n elements out of a universe of 2 w elements, O(n log log w) bits are sufficient to hash monotonically with evaluation time O(log w). Alternatively, we can get space O(n log w) bits with O(1) query time. Both of these data structures improve a straightforward construction with O(n log w) space and O(log w) query time. As a consequence, it is possible to search a sorted table with O(1) accesses to the table (using additional O(n log log w) bits). Our results are based on a structure (of independent interest) that represents a trie in a very compact way, but admits errors. As a further application of the same structure, we show how to compute the predecessor (in the sorted order of S) of an arbitrary element, using O(1) accesses in expectation and an index of O(n log w) bits, improving the trivial result of O(nw) bits. This implies an efficient index for searching a blocked memory.
Optimal static range reporting in one dimension
 IN PROC. 33RD ACM SYMPOSIUM ON THEORY OF COMPUTING (STOC'01)
, 2001
"... ..."
Range mode and range median queries on lists and trees
 In Proceedings of the 14th Annual International Symposium on Algorithms and Computation (ISAAC
, 2003
"... ABSTRACT. We consider algorithms for preprocessing labelled lists and trees so that, for any two nodes u and v we can answer queries of the form: What is the mode or median label in the sequence of labels on the path from u to v. 1 ..."
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Cited by 16 (3 self)
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ABSTRACT. We consider algorithms for preprocessing labelled lists and trees so that, for any two nodes u and v we can answer queries of the form: What is the mode or median label in the sequence of labels on the path from u to v. 1
Confluently Persistent Deques via DataStructural Bootstrapping
 J. of Algorithms
, 1993
"... We introduce datastructural bootstrapping, a technique to design data structures recursively, and use it to design confluently persistent deques. Our data structure requires O(log 3 k) worstcase time and space per deletion, where k is the total number of deque operations, and constant worstcase t ..."
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Cited by 15 (4 self)
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We introduce datastructural bootstrapping, a technique to design data structures recursively, and use it to design confluently persistent deques. Our data structure requires O(log 3 k) worstcase time and space per deletion, where k is the total number of deque operations, and constant worstcase time and space for other operations. Further, the data structure allows a purely functional implementation, with no side effects. This improves a previous result of Driscoll, Sleator, and Tarjan. 1 An extended abstract of this paper was presented at the 4th ACMSIAM Symposium on Discrete Algorithms, 1993. 2 Supported by a Fannie and John Hertz Foundation fellowship, National Science Foundation Grant No. CCR8920505, and the Center for Discrete Mathematics and Theoretical Computer Science (DIMACS) under NSFSTC8809648. 3 Also affiliated with NEC Research Institute, 4 Independence Way, Princeton, NJ 08540. Research at Princeton University partially supported by the National Science Foundatio...
Bounded Ordered Dictionaries in O(log log N) Time and O(n) Space
 Information Processing Letters
, 1990
"... In this paper we show how to implement bounded ordered dictionaries, also called bounded priority queues, in O(log log N) time per operation and O(n) space. Here n denotes the number of elements stored in the dictionary and N denotes the size of the universe. Previously, this time bound required O(N ..."
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Cited by 14 (0 self)
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In this paper we show how to implement bounded ordered dictionaries, also called bounded priority queues, in O(log log N) time per operation and O(n) space. Here n denotes the number of elements stored in the dictionary and N denotes the size of the universe. Previously, this time bound required O(N) space [E77].
MultiMethod Dispatching: A Geometric Approach with Applications to String Matching Problems
, 1999
"... Current object oriented programming languages (OOPLs) rely on monomethod dispatching. Recent research has identified multimethods as a new, powerful feature to be added to OOPLs, and several experimental OOPLs now have multimethods. Their ultimate success and impact in practice depends, among ..."
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Cited by 14 (3 self)
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Current object oriented programming languages (OOPLs) rely on monomethod dispatching. Recent research has identified multimethods as a new, powerful feature to be added to OOPLs, and several experimental OOPLs now have multimethods. Their ultimate success and impact in practice depends, among other things, on whether multimethod dispatching can be supported efficiently. We show that the multimethod dispatching problem can be transformed to a geometric problem on multidimensional integer grids, for which we then develop a data structure that uses nearlinear space and has O(log log n) query time. This gives a solution whose performance almost matches that of the best known algorithm for standard monomethod dispatching. Our geometric data structure has other applications as well, namely in two string matching problems: matching multiple rectangular patterns against a rectangular query text, and approximate dictionary matching with edit distance at most one. Our results f...
Range Selection and Median: Tight Cell Probe Lower Bounds and Adaptive Data Structures
"... Range selection is the problem of preprocessing an input array A of n unique integers, such that given a query (i, j, k), one can report the k’th smallest integer in the subarray A[i], A[i + 1],..., A[j]. In this paper we consider static data structures in the wordRAM for range selection and severa ..."
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Cited by 12 (5 self)
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Range selection is the problem of preprocessing an input array A of n unique integers, such that given a query (i, j, k), one can report the k’th smallest integer in the subarray A[i], A[i + 1],..., A[j]. In this paper we consider static data structures in the wordRAM for range selection and several natural special cases thereof. The first special case is known as range median, which arises when k is fixed to ⌊(j − i + 1)/2⌋. The second case, denoted prefix selection, arises when i is fixed to 0. Finally, we also consider the bounded rank prefix selection problem and the fixed rank range selection problem. In the former, data structures must support prefix selection queries under the assumption that k ≤ κ for some value κ ≤ n given at construction time, while in the latter, data structures must support range selection queries where k is fixed beforehand for all queries. We prove cell probe lower bounds for range selection, prefix selection and range median, stating that any data structure that uses S words of space needs Ω(log n / log(Sw/n)) time to answer a query. In particular, any data structure that uses n log O(1) n space needs Ω(log n / log log n) time to answer a query, and any data structure that supports queries in constant time, needs n 1+Ω(1) space. For data structures that uses n log O(1) n space this matches the best known upper bound. Additionally, we present a linear space data structure that supports range selection queries in O(log k / log log n + log log n) time. Finally, we prove that any data structure that uses S space, needs Ω(log κ / log(Sw/n)) time to answer a bounded rank prefix selection query and Ω(log k / log(Sw/n)) time to answer a fixed rank range selection query. This shows that our data structure is optimal except for small values of k. 1
Efficient Regular Data Structures and Algorithms for Dilation, Location and Proximity Problems
"... In this paper we investigate datastructures obtained by a recursive partitioning of the input domain into regions of equal size. One of the most well known examples of such a structure is the quadtree, used here as a basis for more complex data structures; we also provide multidimensional version ..."
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Cited by 12 (0 self)
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In this paper we investigate datastructures obtained by a recursive partitioning of the input domain into regions of equal size. One of the most well known examples of such a structure is the quadtree, used here as a basis for more complex data structures; we also provide multidimensional versions of the stratified tree by van Emde Boas [20]. We show that under the assumption that the input points have limited precision (i.e. are drawn from the integer grid of size u) these data structures yield efficient solutions to many important problems. In particular, they allow us to achieve O(log log u) time per operation for dynamic approximate nearest neighbor (under insertions and deletions) and exact online closest pair (under insertions only) in any constant dimension. They allow O(log log u) point location in a given planar shape or in its expansion (dilation by a ball of a given radius). Finally, we provide a linear time (optimal) algorithm for computing the expansion of a shape...