Algorithmic Aspects of Semitotal Domination in Graphs

TL;DR

This paper investigates the computational complexity and approximation algorithms for the semitotal domination problem in various classes of graphs, establishing NP-completeness results, polynomial solutions for interval graphs, and approximation bounds.

Contribution

It proves NP-completeness for several graph classes, provides a polynomial algorithm for interval graphs, and analyzes approximation limits and complexity for the problem.

Findings

NP-complete for planar, split, and chordal bipartite graphs

Polynomial-time algorithm for interval graphs

Approximation ratio of 2+3ln(Δ+1) for maximum degree Δ

Abstract

For a graph $G=(V,E)$, a set $D \subseteq V$ is called a semitotal dominating set of $G$ if $D$ is a dominating set of $G$, and every vertex in $D$ is within distance~$2$ of another vertex of~$D$. The \textsc{Minimum Semitotal Domination} problem is to find a semitotal dominating set of minimum cardinality. Given a graph $G$ and a positive integer $k$, the \textsc{Semitotal Domination Decision} problem is to decide whether $G$ has a semitotal dominating set of cardinality at most $k$. The \textsc{Semitotal Domination Decision} problem is known to be NP-complete for general graphs. In this paper, we show that the \textsc{Semitotal Domination Decision} problem remains NP-complete for planar graphs, split graphs and chordal bipartite graphs. We give a polynomial time algorithm to solve the \textsc{Minimum Semitotal Domination} problem in interval graphs. We show that the \textsc{Minimum Semitotal Domination} problem in a graph with maximum degree~$\Delta$ admits an approximation algorithm that achieves the approximation ratio of $2+3\ln(\Delta+1)$, showing that the problem is in the class log-APX. We also show that the \textsc{Minimum Semitotal Domination} problem cannot be approximated within $(1 - \epsilon)\ln |V| $ for any $\epsilon > 0$ unless NP $\subseteq$ DTIME $(|V|^{O(\log \log |V|)})$. Finally, we prove that the \textsc{Minimum Semitotal Domination} problem is APX-complete for bipartite graphs with maximum degree $4$.