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arXiv 1804.02537cs.DS
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列表边着色的紧下界

Tight Lower Bounds for List Edge Coloring

Łukasz Kowalik, Arkadiusz Socała

摘要:

边着色的最快算法是在时间上运行的$2^m n^{O(1)}$,其中$m$和$n$分别是输入图的边和顶点的数量。对于稠密图,此界限变为$2^{Θ(n^2)}$。这是一个有点独特的情况,因为大多数研究的图形问题承认算法运行的时间$2^{O(n\log n)}$。这是一个臭名昭著的公开问题,要么显示一个算法的边着色运行在时间$2^{o(n^2)}$或反驳它,假设指数时间假设(ETH)或其他良好建立的假设。我们注意到,同样的问题也可以被问到列表边着色,这是边着色的一个很好的推广,其中每个边都有一组(通常称为列表)允许的颜色。我们的主要结果表明,列表边着色简单图不承认一个算法运行在时间$2^{o(n^2)}$,除非ETH失败。有趣的是,边着色的算法运行在时间$2^m n^{O(1)}$推广到列表版本没有任何渐近减速。因此,我们的下限基本上是紧的。这也意味着,为了设计一个算法运行在时间$2^{o(n^2)}$的边缘着色,必须利用其特殊功能相比,列表版本。

英文摘要:

The fastest algorithms for edge coloring run in time $2^m n^{O(1)}$, where $m$ and $n$ are the number of edges and vertices of the input graph, respectively. For dense graphs, this bound becomes $2^{Θ(n^2)}$. This is a somewhat unique situation, since most of the studied graph problems admit algorithms running in time $2^{O(n\log n)}$. It is a notorious open problem to either show an algorithm for edge coloring running in time $2^{o(n^2)}$ or to refute it, assuming Exponential Time Hypothesis (ETH) or other well established assumption. We notice that the same question can be asked for list edge coloring, a well-studied generalization of edge coloring where every edge comes with a set (often called a list) of allowed colors. Our main result states that list edge coloring for simple graphs does not admit an algorithm running in time $2^{o(n^2)}$, unless ETH fails. Interestingly, the algorithm for edge coloring running in time $2^m n^{O(1)}$ generalizes to the list version without any asymptotic slow-down. Thus, our lower bound is essentially tight. This also means that in order to design an algorithm running in time $2^{o(n^2)}$ for edge coloring, one has to exploit its special features compared to the list version.

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