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arXiv 1202.4419cs.DMcs.DS
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无爪图的导出不交路

Induced Disjoint Paths in Claw-Free Graphs

Petr A. Golovach, Daniel Paulusma, Erik Jan van Leeuwen

摘要:

路径P1,...,称图G=(V,E)中的Pk是相互诱导的,如果对任意1 <= i < j <= k,Pi和Pj既没有公共点也没有相邻点(可能除了它们的端点).导出不相交路问题是检验一个具有k对指定顶点(si,ti)的图G是否包含k条相互导出的路Pi,使得Pi连接si和ti,i=1,.,K.我们表明,这个问题是固定参数的易处理的无爪图时,参数为k。几个相关的问题,如k-in-a-Path问题,被证明是固定参数易处理的无爪图以及。我们表明,这些结果在某些方向上的改进是不可能的,例如,注意到,诱导不相交路径问题不能有一个多项式核线图(一类无爪图),除非NP \subseteq coNP/聚。而且,对于更一般的K_1,4-free图,即使当k=2时,问题也是NP-完全的.最后,我们证明了Fiala等人的n^O(k)-时间算法对于无爪图是否包含k-顶点图H作为拓扑诱导子式的问题是本质最优的,即使G和H是线图,这个问题也是W[1]-困难的.

英文摘要:

Paths P1,...,Pk in a graph G=(V,E) are said to be mutually induced if for any 1 <= i < j <= k, Pi and Pj have neither common vertices nor adjacent vertices (except perhaps their end-vertices). The Induced Disjoint Paths problem is to test whether a graph G with k pairs of specified vertices (si,ti) contains k mutually induced paths Pi such that Pi connects si and ti for i=1,...,k. We show that this problem is fixed-parameter tractable for claw-free graphs when parameterized by k. Several related problems, such as the k-in-a-Path problem, are proven to be fixed-parameter tractable for claw-free graphs as well. We show that an improvement of these results in certain directions is unlikely, for example by noting that the Induced Disjoint Paths problem cannot have a polynomial kernel for line graphs (a type of claw-free graphs), unless NP \subseteq coNP/poly. Moreover, the problem becomes NP-complete, even when k=2, for the more general class of K_1,4-free graphs. Finally, we show that the n^O(k)-time algorithm of Fiala et al. for testing whether a claw-free graph contains some k-vertex graph H as a topological induced minor is essentially optimal by proving that this problem is W[1]-hard even if G and H are line graphs.

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