Terrain-like graphs: PTASs for guarding weakly-visible polygons and terrains

Stav Ashur, Omrit Filtser, Matthew J. Katz, Rachel Saban

Research output: Contribution to journalArticlepeer-review


A graph G=(V,E) is terrain-like if one can assign a unique integer from the range [1.|V|] to each vertex in V, such that, if both {i,k} and {j,l} are in E, for any i<j<k<l, then so is {i,l}. We present a local-search-based PTAS for minimum dominating set in terrain-like graphs. Then, we observe that, besides the visibility graphs of x-monotone terrains which are terrain-like, so are the visibility graphs of weakly-visible polygons and weakly-visible terrains, immediately implying a PTAS for guarding the vertices of such a polygon or terrain from its vertices. We also present PTASs for continuously guarding the boundary of a WV-polygon or WV-terrain, either from its vertices, or, for a WV-terrain, from arbitrary points on the terrain. Finally, we compare between terrain-like graphs and non-jumping graphs, and also observe that both families admit PTASs for maximum independent set.

Original languageEnglish
Article number101832
Pages (from-to)101832
Number of pages1
JournalComputational Geometry: Theory and Applications
StatePublished - Feb 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2021 Elsevier B.V.


  • Guarding
  • Local search
  • Maximum independent set
  • Minimum dominating set
  • Non-jumping graphs
  • PTAS


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