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arXiv 2007.11495cs.DS
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具有次立方预处理时间的改进距离敏感预言机

Improved Distance Sensitivity Oracles with Subcubic Preprocessing Time

Hanlin Ren

摘要:

我们考虑的问题,建立距离敏感性预言机(DSO)。给定$\{1, 2, \dots, M\}$中一个带边权的有向图$G=(V, E)$,我们需要将其预处理成一个数据结构,并回答以下查询:给定顶点$u,v\in V$和一个失败的顶点或边$f\in (V\cup E)$,输出从$u$到$v$的不经过$f$的最短路径的长度。我们的主要结果是一个简单的DSO与$\tilde{O}(n^{2.7233}M)$预处理时间和$O(1)$查询时间。此外,如果输入图是无向的,则预处理时间可以改进为$\tilde{O}(n^{2.6865}M)$。预处理算法是随机的正确概率$\ge 1-1/n^C$,对于一个常数$C$,可以任意大。以前,有一个具有$\tilde{O}(n^{2.8729}M)$预处理时间和$\operatorname{polylog}(n)$查询时间的DSO [Escherhik和Cohen,STOC'20]。我们的DSO的核心是[Bernstein and Karger,STOC'09]中的以下观察:如果存在具有预处理时间$P$和查询时间$Q$的DSO,则我们可以构造具有预处理时间$P+\tilde{O}(n^2)\cdot Q$和查询时间$O(1)$的DSO。(Here $\tilde{O}(\cdot)$隐藏$\operatorname{polylog}(n)$因子。)

英文摘要:

We consider the problem of building Distance Sensitivity Oracles (DSOs). Given a directed graph $G=(V, E)$ with edge weights in $\{1, 2, \dots, M\}$, we need to preprocess it into a data structure, and answer the following queries: given vertices $u,v\in V$ and a failed vertex or edge $f\in (V\cup E)$, output the length of the shortest path from $u$ to $v$ that does not go through $f$. Our main result is a simple DSO with $\tilde{O}(n^{2.7233}M)$ preprocessing time and $O(1)$ query time. Moreover, if the input graph is undirected, the preprocessing time can be improved to $\tilde{O}(n^{2.6865}M)$. The preprocessing algorithm is randomized with correct probability $\ge 1-1/n^C$, for a constant $C$ that can be made arbitrarily large. Previously, there is a DSO with $\tilde{O}(n^{2.8729}M)$ preprocessing time and $\operatorname{polylog}(n)$ query time [Chechik and Cohen, STOC'20]. At the core of our DSO is the following observation from [Bernstein and Karger, STOC'09]: if there is a DSO with preprocessing time $P$ and query time $Q$, then we can construct a DSO with preprocessing time $P+\tilde{O}(n^2)\cdot Q$ and query time $O(1)$. (Here $\tilde{O}(\cdot)$ hides $\operatorname{polylog}(n)$ factors.)

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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