Computing maximum independent set on outerstring graphs and their relatives.

Prosenjit Bose, Paz Carmi, J. Mark Keil, Anil Maheshwari, Saeed Mehrabi, Debajyoti Mondal, Michiel Smid

Research output: Contribution to journalArticlepeer-review


A graph G with n vertices is called an outerstring graph if it has an intersection representation with a set of n curves inside a disk such that one endpoint of every curve is attached to the boundary of the disk. Given an outerstring graph representation of G with s segments, a Maximum Independent Set () of G can be computed in time (Keil et al. (2017) [22]).

We examine the fine-grained complexity of the problem on some well-known outerstring representations (e.g., line segments, -shapes, etc.), where the strings are of constant size. We show that computing on grounded segment and grounded square- representations is at least as hard as computing on circle graph representations. Note that no -time algorithm, , is known for computing on circle graphs. For the grounded string representations, where the strings are y-monotone simple polygonal paths of constant length with segments at integral coordinates, we solve in time and show this to be the best possible under the Strong Exponential Time Hypothesis. For the intersection graph of n -shapes in the plane, we give a -approximation algorithm for (where denotes the size of an optimal solution), improving the previously best-known -approximation algorithm of Biedl and Derka (WADS 2017).
Original languageEnglish
Pages (from-to)101852
Number of pages1
JournalComputational Geometry: Theory and Applications
StatePublished - 2022


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