Helly Circular-Arc Graph Isomorphism Is in Logspace

  • Johannes Köbler
  • Sebastian Kuhnert
  • Oleg Verbitsky
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8087)


We present logspace algorithms for the canonical labeling problem and the representation problem of Helly circular-arc (HCA) graphs. The first step is a reduction to canonical labeling and representation of interval intersection matrices. In a second step, the Δ trees employed in McConnell’s linear time representation algorithm for interval matrices are adapted to the logspace setting and endowed with additional information to allow canonization. As a consequence, the isomorphism and recognition problems for HCA graphs turn out to be logspace complete.


Interval Graph Interval Matrix Interval Representation Interval System Interval Matrice 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Johannes Köbler
    • 1
  • Sebastian Kuhnert
    • 1
  • Oleg Verbitsky
    • 1
  1. 1.Institut für InformatikHumboldt-Universität zu BerlinGermany

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