Journal of Combinatorial Theory Series B ( IF 1.2 ) Pub Date : 2019-07-19 , DOI: 10.1016/j.jctb.2019.06.004 Jie Han , Andrew Treglown
Given two k-graphs H and F, a perfect F-packing in H is a collection of vertex-disjoint copies of F in H which together cover all the vertices in H. In the case when F is a single edge, a perfect F-packing is simply a perfect matching. For a given fixed F, it is often the case that the decision problem whether an n-vertex k-graph H contains a perfect F-packing is NP-complete. Indeed, if , the corresponding problem for perfect matchings is NP-complete [17], [7] whilst if the problem is NP-complete in the case when F has a component consisting of at least 3 vertices [14].
In this paper we give a general tool which can be used to determine classes of (hyper)graphs for which the corresponding decision problem for perfect F-packings is polynomial time solvable. We then give three applications of this tool: (i) Given , we give a minimum ℓ-degree condition for which it is polynomial time solvable to determine whether a k-graph satisfying this condition has a perfect matching; (ii) Given any graph F we give a minimum degree condition for which it is polynomial time solvable to determine whether a graph satisfying this condition has a perfect F-packing; (iii) We also prove a similar result for perfect K-packings in k-graphs where K is a k-partite k-graph.
For a range of values of (i) resolves a conjecture of Keevash, Knox and Mycroft [20]; (ii) answers a question of Yuster [47] in the negative; whilst (iii) generalises a result of Keevash, Knox and Mycroft [20]. In many cases our results are best possible in the sense that lowering the minimum degree condition means that the corresponding decision problem becomes NP-complete.
中文翻译:
稠密超图的完美匹配和堆积的复杂性
给定两个ķ -graphs ^ h和˚F,完美˚F在分装^ h是顶点不相交的副本的集合˚F在^ h一起覆盖所有顶点^ h。在F是单边的情况下,完美的F包装只是完美的匹配。对于给定的固定F,通常情况下,n-顶点k图H是否包含理想F堆积的决策问题是NP完全的。确实,如果,则完美匹配的相应问题是NP完全[17],[7],而如果 当F的分量至少由3个顶点组成时,问题是NP完全的[14]。
在本文中,我们提供了一种通用工具,可用于确定(超)图的类,对于这些类,理想的F堆积的相应决策问题是多项式时间可解的。然后,我们给出该工具的三个应用:(i)给定,我们给出一个最小ℓ度条件,对于该条件,可以通过多项式时间来确定满足该条件的k图是否具有完美匹配;(ii)给定任何图F,我们给出一个最小次数条件,对于该条件,可以确定多项式时间,以确定满足该条件的图是否具有理想的F堆积;(三)我们还证明了完美类似的结果ķ在-packings ķ -graphs其中ķ是ķ -partite ķ -图。
对于以下范围的值 (i)解决了Keevash,Knox和Mycroft的猜想[20];(ii)否定回答Yuster [47]的问题;(iii)概括了Keevash,Knox和Mycroft的结果[20]。在许多情况下,从降低最低程度条件意味着相应的决策问题变为NP完全的意义上说,我们的结果是最好的。