Dichotomy study of the Steiner tree problem in split-like graphs
Abstract
Given a connected graph and a terminal set , the minimum Steiner tree problem (ST) asks for a tree that spans all of with at most vertices from , for some integer . A \emph{split graph} is a graph which can be partitioned into a clique and an independent set. It is known from (Garey et al.,1977) that ST is NP-complete, even for split graphs . We introduce the class of split-like graphs which unifies several known graph classes like bipartite graphs, split graphs, and bisplit graphs, allowing for a cohesive study across multiple structural constraints. We investigate the computational complexity of the Steiner tree problem under structural constraints, specifically -free, bounded diameter, chordality and star-convexity. Through reductions (primarily from Exact-3-Cover and its variants), the paper establishes a series of dichotomy results. It precisely gives the boundary for -free bipartite graphs: ST is in P for and NP-complete for ; whereas on -free bisplit graphs, ST is in P for any fixed . On bisplit graphs, the Steiner tree problem admits a polynomial-time solution when the diameter is 2. In contrast, for diameters 3 and 4, the problem is NP-complete. The problem is NP-complete under star convexity constraints on the independent set. When star convexity is imposed on the -clique side, the problem is solvable in polynomial time. The problem is NP-complete on chordal bipartite graphs and chordal split graphs (i.e., split graphs themselves), while polynomial-time algorithms exist for other subclasses of split-like graphs.
Cite
@article{arxiv.2605.29540,
title = {Dichotomy study of the Steiner tree problem in split-like graphs},
author = {Jyothish S and Sadagopan Narasimhan},
journal= {arXiv preprint arXiv:2605.29540},
year = {2026}
}