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Lions and Contamination: Monotone Clearings

Authors Daniel Bertschinger, Meghana M. Reddy, Enrico Mann

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Author Details

Daniel Bertschinger
  • Department of Computer Science, ETH Zürich, Switzerland
Meghana M. Reddy
  • Department of Computer Science, ETH Zürich, Switzerland
Enrico Mann
  • Department of Computer Science, ETH Zürich, Switzerland

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Daniel Bertschinger, Meghana M. Reddy, and Enrico Mann. Lions and Contamination: Monotone Clearings. In 18th Scandinavian Symposium and Workshops on Algorithm Theory (SWAT 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 227, pp. 17:1-17:11, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)


We consider a special variant of a pursuit-evasion game called lions and contamination. In a graph whose vertices are originally contaminated, a set of lions walk around the graph and clear the contamination from every vertex they visit. The contamination, however, simultaneously spreads to any adjacent vertex not occupied by a lion. We study the relationship between different types of clearings of graphs, such as clearings which do not allow recontamination, clearings where at most one lion moves at each time step and clearings where lions are forbidden to be stacked on the same vertex. We answer several questions raised by Adams et al. [H. Adams et al., 2020].

Subject Classification

ACM Subject Classification
  • Mathematics of computing → Graph algorithms
  • Mathematics of computing → Combinatorial algorithms
  • Algorithmic Games
  • Pursuit-Evasion Games
  • Graph Contamination
  • Clearings


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