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arXiv 2008.02060cs.DS
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关于最小割的一个新算法的注记

A Note on a Recent Algorithm for Minimum Cut

Paweł Gawrychowski, Shay Mozes, Oren Weimann

摘要:

给定一个具有$m$边和$n$顶点的无向边赋权图$G=(V,E)$,最小割问题要求找到一个顶点子集$S$,使得$S$和$V \setminus S$之间所有边的总权最小. Karger的长期$O(m \log^3 n)$时间随机算法这个问题最近在两个独立的工作$O(m \log^2 n)$ [ICALP'20]和$O(m \log^2 n + n\log^5 n)$ [STOC'20]。这两种算法使用不同的方法和技术。特别是,虽然前者更快,后者的优点是,它可以用来获得有效的算法在切割查询和计算的流模型。本文给出了如何将[STOC'20]的算法简化和改进为$O(m \log^2 n + n\log^3 n)$。我们得到这一点,通过替换随机算法,给定一个生成树$T$的$G$,发现在$O(m \log n+n\log^4 n)$时间的最小切割$G$,2-尊重(削减两个边缘)$T$与一个简单的$O(m \log n+n\log^2 n)$时间确定性算法相同的问题。

英文摘要:

Given an undirected edge-weighted graph $G=(V,E)$ with $m$ edges and $n$ vertices, the minimum cut problem asks to find a subset of vertices $S$ such that the total weight of all edges between $S$ and $V \setminus S$ is minimized. Karger's longstanding $O(m \log^3 n)$ time randomized algorithm for this problem was very recently improved in two independent works to $O(m \log^2 n)$ [ICALP'20] and to $O(m \log^2 n + n\log^5 n)$ [STOC'20]. These two algorithms use different approaches and techniques. In particular, while the former is faster, the latter has the advantage that it can be used to obtain efficient algorithms in the cut-query and in the streaming models of computation. In this paper, we show how to simplify and improve the algorithm of [STOC'20] to $O(m \log^2 n + n\log^3 n)$. We obtain this by replacing a randomized algorithm that, given a spanning tree $T$ of $G$, finds in $O(m \log n+n\log^4 n)$ time a minimum cut of $G$ that 2-respects (cuts two edges of) $T$ with a simple $O(m \log n+n\log^2 n)$ time deterministic algorithm for the same problem.

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