Testing isomorphism of circular-arc graphs -- Hsu's approach revisited
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Circular-arc graphs are intersection graphs of arcs on the circle. The aim of our work is to present a polynomial time algorithm testing whether two circular-arc graphs are isomorphic. To accomplish our task we construct decomposition trees, which are the structures representing all normalized intersection models of circular-arc graphs. Normalized models reflect the neighbourhood relation in circular-arc graphs and can be seen as their canonical representations; in particular, every intersection model can be easily transformed into a normalized one. Our work adapts and appropriately extends the previous work on the similar topic done by Hsu [SIAM J. Comput. 24(3), 411--439, (1995)]. In his work, Hsu developed decomposition trees representing all normalized models of circular-arc graphs. However due to the counterexample given in [Discrete Math. Theor. Comput. Sci., 15(1), 157--182, 2013], his decomposition trees can not be used by algorithms testing isomorphism of circular-arc graphs.
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