A recognition algorithm for adjusted interval digraphs

10/15/2018

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by   Asahi Takaoka, et al.

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Min orderings give a vertex ordering characterization, common to some graphs and digraphs such as interval graphs, complements of threshold tolerance graphs (known as co-TT graphs), and two-directional orthogonal ray graphs. An adjusted interval digraph is a reflexive digraph that has a min ordering. Adjusted interval digraph can be recognized in O(n^4) time, where n is the number of vertices of the given graph. Finding a more efficient algorithm is posed as an open question. This note provides a new recognition algorithm with running time O(n^3). The algorithm produces a min ordering if the given graph is an adjusted interval digraph.