论文标题
在围绕围环以及令牌滑动和令牌跳跃的参数化复杂性
On girth and the parameterized complexity of token sliding and token jumping
论文作者
论文摘要
在令牌跳跃问题中,我们给出了图$ g =(v,e)$和两个独立的$ s $和$ g $的$ t $ $ g $,每个大小$ k \ geq 1 $。目的是确定是否存在$ k $尺寸的独立集$ g $,$ \ langle s_0,s_1,\ ldots,s_ \ ell \ rangle $,以便每$ i $,$ | s_i | = k $,$ s_i $是一个独立集,$ s = s_0 $,$ s_ \ ell = t $,$ |s_iδs_{i+1} | = 2 $。换句话说,如果我们将每个独立集合视为$ g $顶点子集的代币集合,那么问题就会要求单个令牌跳高将$ s $转换为$ t $的独立集,以维持集合的独立性。已知该问题在非常有限的图类别上是PSPACE完整的,例如平面边界度图和有界带宽的图。一个密切相关的问题是令牌滑动问题,而不是让令牌跳到图表的任何顶点,我们需要沿图的边缘沿图的幻灯片。在上述图类别上,也已知令牌滑动是PSPACE完整的。我们研究了几个图类别上这两个问题的参数化复杂性,重点是从输入图中排除某些周期的效果。特别是,我们表明,当通过$ k $参数化时,令牌滑动和令牌跳跃都是固定参数可在$ C_4 $ -FREE双方图上进行处理。对于代币跳跃,我们实际上表明,该问题在$ \ {C_3,C_4 \} $上允许多项式内核 - 免费图形。在令牌滑动的情况下,我们还表明,该问题在界限图上接受了多项式内核。我们认为这两种结果都具有独立的兴趣。我们通过表明,对于任何常数$ p \ geq 4 $,这两个问题都是$ \ {c_4,\ dots,c_p \} $ - 免费的图形和令牌滑动w [1] -HARD即使在Biptite Graphs上。
In the Token Jumping problem we are given a graph $G = (V,E)$ and two independent sets $S$ and $T$ of $G$, each of size $k \geq 1$. The goal is to determine whether there exists a sequence of $k$-sized independent sets in $G$, $\langle S_0, S_1, \ldots, S_\ell \rangle$, such that for every $i$, $|S_i| = k$, $S_i$ is an independent set, $S = S_0$, $S_\ell = T$, and $|S_i ΔS_{i+1}| = 2$. In other words, if we view each independent set as a collection of tokens placed on a subset of the vertices of $G$, then the problem asks for a sequence of independent sets which transforms $S$ to $T$ by individual token jumps which maintain the independence of the sets. This problem is known to be PSPACE-complete on very restricted graph classes, e.g., planar bounded degree graphs and graphs of bounded bandwidth. A closely related problem is the Token Sliding problem, where instead of allowing a token to jump to any vertex of the graph we instead require that a token slides along an edge of the graph. Token Sliding is also known to be PSPACE-complete on the aforementioned graph classes. We investigate the parameterized complexity of both problems on several graph classes, focusing on the effect of excluding certain cycles from the input graph. In particular, we show that both Token Sliding and Token Jumping are fixed-parameter tractable on $C_4$-free bipartite graphs when parameterized by $k$. For Token Jumping, we in fact show that the problem admits a polynomial kernel on $\{C_3,C_4\}$-free graphs. In the case of Token Sliding, we also show that the problem admits a polynomial kernel on bipartite graphs of bounded degree. We believe both of these results to be of independent interest. We complement these positive results by showing that, for any constant $p \geq 4$, both problems are W[1]-hard on $\{C_4, \dots, C_p\}$-free graphs and Token Sliding remains W[1]-hard even on bipartite graphs.