论文标题
在方向图的船体和间隔数字上
On the hull and interval numbers of oriented graphs
论文作者
论文摘要
在这项工作中,对于给定的图形$ d $,我们分别研究其间隔和船体数量,在定向的大地测量,P3和P3*凸度中。最后一个,我们认为在本文中是正式定义和首次研究的,尽管其无方向版本在文献中是众所周知的。 关于界限的界限,对于强烈的图形D和定向的测量凸度,我们证明了$ ohng(d)\ leq m(d)-n(d)-n(d)+2 $,并且至少有一个使$ ohng(d)= m(d)= m(d)-n(d)-n(d)$。我们还确定了这三个凸度的船体数的确切值,这意味着要计算它们的多项式时间算法。这些结果使我们能够推断出多项式时间算法,以计算$ ohnp(d)$当$ d $的基础图分开或cobipartite时。 此外,我们通过证明,如果确定$ oing(d)\ leq k $还是$ ohng(d)\ leq k $是np-hard还是w [i] hard由$ k $进行参数化的,则对于某些$ i \ in \ in \ mathbb {z _+^*} $,即使是$ d的$ bip nounder dragns in ynunder n ynunder nounder dograuts。接下来,我们证明确定$ ohnp(d)\ leq k $还是$ ohnps(d)\ leq k $是w [2] hard hard由$ k $进行了参数,即使$ d $是acyclic,并且其基础图是bipartite;决定$ ohng(d)\ leq k $是否是$ k $的参数,即使$ d $是acyclic;决定$ oinp(d)\ leq k $还是$ oinps(d)\ leq k $是np complete,即使$ d $没有定向周期,并且$ d $的基础图是弦式二级组合图;并且决定$ oinp(d)\ leq k $还是$ oinps(d)\ leq k $是w [2] - hard hard由$ k $进行了参数化,即使$ d $的基础图被拆分。 最后,还认为,可以通过使用Courcelle的定理以三次计算的分数计算定向P3和P3*中的间隔和船体数。
In this work, for a given oriented graph $D$, we study its interval and hull numbers, respectively, in the oriented geodetic, P3 and P3* convexities. This last one, we believe to be formally defined and first studied in this paper, although its undirected version is well-known in the literature. Concerning bounds, for a strongly oriented graph D, and the oriented geodetic convexity, we prove that $ohng(D)\leq m(D)-n(D)+2$ and that there is at least one such that $ohng(D) = m(D)-n(D)$. We also determine exact values for the hull numbers in these three convexities for tournaments, which imply polynomial-time algorithms to compute them. These results allow us to deduce polynomial-time algorithms to compute $ohnp(D)$ when the underlying graph of $D$ is split or cobipartite. Moreover, we provide a meta-theorem by proving that if deciding whether $oing(D)\leq k$ or $ohng(D)\leq k$ is NP-hard or W[i]-hard parameterized by $k$, for some $i\in\mathbb{Z_+^*}$, then the same holds even if the underlying graph of $D$ is bipartite. Next, we prove that deciding whether $ohnp(D)\leq k$ or $ohnps(D)\leq k$ is W[2]-hard parameterized by $k$, even if $D$ is acyclic and its underlying graph is bipartite; that deciding whether $ohng(D)\leq k$ is W[2]-hard parameterized by $k$, even if $D$ is acyclic; that deciding whether $oinp(D)\leq k$ or $oinps(D)\leq k$ is NP-complete, even if $D$ has no directed cycles and the underlying graph of $D$ is a chordal bipartite graph; and that deciding whether $oinp(D)\leq k$ or $oinps(D)\leq k$ is W[2]-hard parameterized by $k$, even if the underlying graph of $D$ is split. Finally, also argue that the interval and hull numbers in the oriented P3 and P3* convexities can be computed in cubic time for graphs of bounded clique-width by using Courcelle's theorem.