arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1108.1983cs.DS
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排列与函数的简洁表示

Succinct Representations of Permutations and Functions

J. Ian Munro, Rajeev Raman, Venkatesh Raman, S. Srinivasa Rao

摘要:

我们研究了在{0,..上简洁地表示任意置换π的问题,n-1},使得π^k(i)可以针对任意i和任意(正或负)整数幂k快速计算。对于任何正的常数ε<= 1,一个取(1+ε)n lg n + O(1)位的表示足以在常数时间内计算任意幂。采用最优\ceil{\lg n!} + o(n)位的表示可用于在O(lg n / lg lg n)时间内计算任意幂。然后,我们考虑更一般的问题,即简洁地表示任意函数f:[n] \rightarrow [n],使得f^k(i)可以对任意i和任意整数次幂k快速计算。我们给出了一个表示,对于任意的正常数ε<= 1,它需要(1+ε)nlgn + O(1)比特,并且在常数时间内计算任意的正幂.它也可以用来计算f^k(i),对于任何负整数k,最优O(1+ 1)|f^k(i)|)时间。我们把重点放在冗余,或空间以外的信息理论的下限,数据结构使用,以有效地支持操作。最近,人们对数据结构的冗余度提出了许多下限。这些下界证实了我们的一些解的时空最优性。此外,我们的一个结构的冗余度“超过”Golynski最近的下限[Golynski,SODA 2009],从而证明了这个下限的局限性。

英文摘要:

We investigate the problem of succinctly representing an arbitrary permutation, π, on {0,...,n-1} so that π^k(i) can be computed quickly for any i and any (positive or negative) integer power k. A representation taking (1+ε) n lg n + O(1) bits suffices to compute arbitrary powers in constant time, for any positive constant ε<= 1. A representation taking the optimal \ceil{\lg n!} + o(n) bits can be used to compute arbitrary powers in O(lg n / lg lg n) time. We then consider the more general problem of succinctly representing an arbitrary function, f: [n] \rightarrow [n] so that f^k(i) can be computed quickly for any i and any integer power k. We give a representation that takes (1+ε) n lg n + O(1) bits, for any positive constant ε<= 1, and computes arbitrary positive powers in constant time. It can also be used to compute f^k(i), for any negative integer k, in optimal O(1+|f^k(i)|) time. We place emphasis on the redundancy, or the space beyond the information-theoretic lower bound that the data structure uses in order to support operations efficiently. A number of lower bounds have recently been shown on the redundancy of data structures. These lower bounds confirm the space-time optimality of some of our solutions. Furthermore, the redundancy of one of our structures "surpasses" a recent lower bound by Golynski [Golynski, SODA 2009], thus demonstrating the limitations of this lower bound.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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