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arXiv 1409.4935cs.DSmath.CO
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更快地找到偶数子图

Finding Even Subgraphs Even Faster

Prachi Goyal, Pranabendu Misra, Fahad Panolan, Geevarghese Philip, Saket Saurabh

摘要:

下面的问题是最近参数化复杂性领域研究的焦点:给定一个在$n$顶点上的输入图(有向图)和一个正整数参数$k$,找出是否存在$k$的边(弧),如果删除这些边,图满足某些指定的奇偶性约束。特别是,当目标是获得一个连通图,其中所有的顶点都有偶数度-其中得到的图是\emph{Eulerian} -这个问题被称为无向欧拉边删除。有向图中的相应问题,其中所得到的图应该是强连通的,并且每个顶点应该具有与其出度相同的入度,称为有向欧拉边删除。Cygan等人[ \emph{Algorithmica, 2014} ]证明了这些问题是固定参数可处理的(FPT),并给出了具有运行时间的算法$2^{O(k \log k)}n^{O(1)}$ .他们还问,作为一个开放的问题,是否存在FPT算法,解决这些问题的时间$2^{O(k)}n^{O(1)}$。在本文中,我们回答他们的问题是肯定的:使用技术计算\emph{representative families of co-graphic matroids},我们设计的算法,解决这些问题的时间$2^{O(k)}n^{O(1)}$。我们对这些问题的关键见解是将解视为一个上图拟阵的独立集。我们相信,这种观点/方法将是有用的,在其他问题中,需要满足的约束之一是连接。

英文摘要:

Problems of the following kind have been the focus of much recent research in the realm of parameterized complexity: Given an input graph (digraph) on $n$ vertices and a positive integer parameter $k$, find if there exist $k$ edges (arcs) whose deletion results in a graph that satisfies some specified parity constraints. In particular, when the objective is to obtain a connected graph in which all the vertices have even degrees---where the resulting graph is \emph{Eulerian}---the problem is called Undirected Eulerian Edge Deletion. The corresponding problem in digraphs where the resulting graph should be strongly connected and every vertex should have the same in-degree as its out-degree is called Directed Eulerian Edge Deletion. Cygan et al. [\emph{Algorithmica, 2014}] showed that these problems are fixed parameter tractable (FPT), and gave algorithms with the running time $2^{O(k \log k)}n^{O(1)}$. They also asked, as an open problem, whether there exist FPT algorithms which solve these problems in time $2^{O(k)}n^{O(1)}$. In this paper we answer their question in the affirmative: using the technique of computing \emph{representative families of co-graphic matroids} we design algorithms which solve these problems in time $2^{O(k)}n^{O(1)}$. The crucial insight we bring to these problems is to view the solution as an independent set of a co-graphic matroid. We believe that this view-point/approach will be useful in other problems where one of the constraints that need to be satisfied is that of connectivity.

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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