论文标题

删除到分散的图类别II-改进的删除fpt算法与成对的图类类

Deletion to Scattered Graph Classes II -- Improved FPT Algorithms for Deletion to Pairs of Graph Classes

论文作者

Jacob, Ashwin, Majumdar, Diptapriyo, Raman, Venkatesh

论文摘要

令$π$为遗传图。删除到$π$的问题,作为输入$ g $,并要求从$ g $中删除的最低数字(或固定整数$ k $)的顶点,以便所得的图属于$π$。这是一个充分研究的问题,包括近似值和参数化复杂性。最近,对问题的自然扩展进行了研究,在我们获得有限的遗传图类别的情况下,目标是确定是否可以从给定的图中删除$ k $的顶点,以使所得图的连接组件属于给定的遗传图一类。只要给定的遗传图类的删除问题是固定参数可进行的,并且在任何图形类中的属性都可以在计数单次二阶(CMSO)逻辑中表达,则该问题被证明是fpt。虽然使用一些黑匣子定理显示了这一点,但是当每个遗传图类别都有有限的禁止集时,显示了更快的算法。在本文中,我们对成对的特定图形类($π_1,π_2$)进行深入研究,其中我们希望所得图的连接组件属于属于的组件,并设计更简单,更有效的FPT算法。我们为满足某些条件的一对图类别(可能具有无限禁止的集合)设计了一般的FPT算法和近似算法(可能具有无限禁止集)。这些算法涵盖了几双流行的图类。我们的算法对分支技术进行了非平凡的使用,作为黑匣子,fpt算法用于删除单个图形类别。

Let $Π$ be a hereditary graph class. The problem of deletion to $Π$, takes as input a graph $G$ and asks for a minimum number (or a fixed integer $k$) of vertices to be deleted from $G$ so that the resulting graph belongs to $Π$. This is a well-studied problem in paradigms including approximation and parameterized complexity. Recently, the study of a natural extension of the problem was initiated where we are given a finite set of hereditary graph classes, and the goal is to determine whether $k$ vertices can be deleted from a given graph so that the connected components of the resulting graph belong to one of the given hereditary graph classes. The problem is shown to be FPT as long as the deletion problem to each of the given hereditary graph classes is fixed-parameter tractable, and the property of being in any of the graph classes is expressible in the counting monodic second order (CMSO) logic. While this was shown using some black box theorems, faster algorithms were shown when each of the hereditary graph classes has a finite forbidden set. In this paper, we do a deep dive on pairs of specific graph classes ($Π_1, Π_2$) in which we would like the connected components of the resulting graph to belong to, and design simpler and more efficient FPT algorithms. We design a general FPT algorithm and approximation algorithm for pairs of graph classes (possibly having infinite forbidden sets) satisfying certain conditions. These algorithms cover several pairs of popular graph classes. Our algorithm makes non-trivial use of the branching technique and as a black box, FPT algorithms for deletion to individual graph classes.

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