arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.10790cs.DS
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5-着色和6-着色的$2^n$障碍的突破

Breaking the $2^n$ barrier for 5-coloring and 6-coloring

Or Zamir

摘要:

着色问题(即,计算图的色数)可以在$O^*(2^n)$时间内解决,如Björklund,Husfeldt和Koivisto在2009年所示。对于$k=3,4$,已知用于$k$着色问题的更好的算法。$3$ -着色可以在$O(1.33^n)$时间内求解(Beigel和Eppstein,2005),而$4$ -着色可以在$O(1.73^n)$时间内求解(Fomin,Gaspers和Saurabh,2007)。令人惊讶的是,对于$k>4$,已知没有超过一般$O^*(2^n)$的改进。我们证明了对于某些$\varepsilon>0$,$5$ -着色和$6$ -着色也可以在$O\left(\left(2-\varepsilon\right)^n\right)$时间内求解.作为关键的一步,我们获得了一个指数的改进计算一个非常大的图族的色数。特别地,对于任何常数$Δ,α>0$,对于某些$\varepsilon = \varepsilon_{Δ,α} > 0$,至少具有度最多为$Δ$的$α\cdot n$顶点的图的色数可以在$O\left(\left(2-\varepsilon\right)^n\right)$时间内计算。这一陈述推广了以前关于有界度图(Björklund,Husfeldt,Kaski和Koivisto,2010)和有界平均度图(Golovnev,Kulikov和Mihajilin,2016)的结果。我们将上述陈述推广到列表着色,即使对于有界度图的情况,也没有以前的改进。

英文摘要:

The coloring problem (i.e., computing the chromatic number of a graph) can be solved in $O^*(2^n)$ time, as shown by Björklund, Husfeldt and Koivisto in 2009. For $k=3,4$, better algorithms are known for the $k$-coloring problem. $3$-coloring can be solved in $O(1.33^n)$ time (Beigel and Eppstein, 2005) and $4$-coloring can be solved in $O(1.73^n)$ time (Fomin, Gaspers and Saurabh, 2007). Surprisingly, for $k>4$ no improvements over the general $O^*(2^n)$ are known. We show that both $5$-coloring and $6$-coloring can also be solved in $O\left(\left(2-\varepsilon\right)^n\right)$ time for some $\varepsilon>0$. As a crucial step, we obtain an exponential improvement for computing the chromatic number of a very large family of graphs. In particular, for any constants $Δ,α>0$, the chromatic number of graphs with at least $α\cdot n$ vertices of degree at most $Δ$ can be computed in $O\left(\left(2-\varepsilon\right)^n\right)$ time, for some $\varepsilon = \varepsilon_{Δ,α} > 0$. This statement generalizes previous results for bounded-degree graphs (Björklund, Husfeldt, Kaski, and Koivisto, 2010) and graphs with bounded average degree (Golovnev, Kulikov and Mihajilin, 2016). We generalize the aforementioned statement to List Coloring, for which no previous improvements are known even for the case bounded-degree graphs.

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