On the Cop Number of String Graphs

Authors Sandip Das, Harmender Gahlawat

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Author Details

Sandip Das
  • Indian Statistical Institute, Kolkata, India
Harmender Gahlawat
  • Ben-Gurion University of the Negev, Beer-Sheva, Israel


We thank Uma kant Sahoo, Dibyayan Chakraborty, and Florent Foucaud for initial discussions on the topic of this paper.

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Sandip Das and Harmender Gahlawat. On the Cop Number of String Graphs. In 33rd International Symposium on Algorithms and Computation (ISAAC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 248, pp. 45:1-45:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


Cops and Robber is a well-studied two-player pursuit-evasion game played on a graph, where a group of cops tries to capture the robber. The cop number of a graph is the minimum number of cops required to capture the robber. We show that the cop number of a string graph is at most 13, improving upon a result of Gavenčiak et al. [Eur. J. of Comb. 72, 45-69 (2018)]. Using similar techniques, we also show that four cops have a winning strategy for a variant of Cops and Robber, named Fully Active Cops and Robber, on planar graphs, addressing an open question of Gromovikov et al. [Austr. J. Comb. 76(2), 248-265 (2020)].

Subject Classification

ACM Subject Classification
  • Mathematics of computing → Graph algorithms
  • Cop number
  • string graphs
  • intersection graphs
  • planar graphs
  • pursuit-evasion games


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