论文标题
定向图中的减少APSP与自适应对手
Decremental APSP in Directed Graphs Versus an Adaptive Adversary
论文作者
论文摘要
给定有向图的$ g =(v,e)$,在$ g $和$ g $和$ n = | v | $的初始版本中经过一系列在线边缘删除序列,我们考虑在$ g $中维护全对最短路径(APSP)的问题。 尽管这个问题已经在一系列研究[ACM'81,focs'99,focs'01,stoc'02,stoc'02,stoc'03,swat'04,stoc'13]中进行了研究,并且$(1+ε)$的问题 - 大约 - 大约溶于近更新的更新时间$ \ time $ \ timps $ \ tiLdeLdildeL $ $ \ timne(mn) [Stoc'13],问题主要是在遗忘对手的背景下研究的,该问题假设对手在启动算法之前修复了更新序列。 在本文中,我们在对手具有自适应的情况下在问题上取得了重大进展,即可以将更新顺序基于数据结构查询的输出。我们介绍了适合不同设置的三个新数据结构: 我们首先提出确定性的数据结构,该结构保持确切的距离,其中总更新时间$ \ tilde {o}(n^3)$。 我们还提出了一个确定性数据结构,该结构维护$(1+ε)$ - 近似距离估计值,总更新时间$ \ tilde o(\ sqrt {m} n^2/ε)$,对于稀疏图为$ \ tilde o(n^{2+1/2}/ε)$。 最后,我们提出了一个随机$(1+ε)$ - 与自适应对手有关的近似数据结构;它的总更新时间为$ \ tilde o(m^{2/3} n^{5/3} + n^{8/3}/(m^{1/3}ε^2)$,对于稀疏图为$ \ tilde o(n^{2 + 1/3})$。 我们的确切数据结构与Baswana等人最佳随机数据结构的总更新时间匹配。 [stoc'02]并在几乎最佳的时间内保持距离矩阵。对于具有$ \ tilde {o}(Mn^2)的自适应对手的最佳数据结构,我们的近似数据结构改进了$总更新时间[JACM'81,STOC'03]。
Given a directed graph $G = (V,E)$, undergoing an online sequence of edge deletions with $m$ edges in the initial version of $G$ and $n = |V|$, we consider the problem of maintaining all-pairs shortest paths (APSP) in $G$. Whilst this problem has been studied in a long line of research [ACM'81, FOCS'99, FOCS'01, STOC'02, STOC'03, SWAT'04, STOC'13] and the problem of $(1+ε)$-approximate, weighted APSP was solved to near-optimal update time $\tilde{O}(mn)$ by Bernstein [STOC'13], the problem has mainly been studied in the context of oblivious adversaries, which assumes that the adversary fixes the update sequence before the algorithm is started. In this paper, we make significant progress on the problem in the setting where the adversary is adaptive, i.e. can base the update sequence on the output of the data structure queries. We present three new data structures that fit different settings: We first present a deterministic data structure that maintains exact distances with total update time $\tilde{O}(n^3)$. We also present a deterministic data structure that maintains $(1+ε)$-approximate distance estimates with total update time $\tilde O(\sqrt{m} n^2/ε)$ which for sparse graphs is $\tilde O(n^{2+1/2}/ε)$. Finally, we present a randomized $(1+ε)$-approximate data structure which works against an adaptive adversary; its total update time is $\tilde O(m^{2/3}n^{5/3} + n^{8/3}/(m^{1/3}ε^2))$ which for sparse graphs is $\tilde O(n^{2+1/3})$. Our exact data structure matches the total update time of the best randomized data structure by Baswana et al. [STOC'02] and maintains the distance matrix in near-optimal time. Our approximate data structures improve upon the best data structures against an adaptive adversary which have $\tilde{O}(mn^2)$ total update time [JACM'81, STOC'03].