Abstract
An opposition graph is a graph whose edges can be acyclically oriented in such a way that every chordless path on four vertices has its extreme edges both pointing in or pointing out. A strict quasi-parity graph is a graphG such that every induced subgraphH ofG either is a clique or else contains a pair of vertices which are not endpoints of an odd (number of edges) chordless path ofH. The perfection of opposition graphs and strict quasi-parity graphs was established respectively by Olariu and Meyniel. We show here that opposition graphs are strict quasi-parity graphs.
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The second author acknowledges the support of the Air Force Office of Scientific Research under grant number AFOSR 0271 to Rutgers University.
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Hoàng, C.T., Maffray, F. Opposition graphs are strict quasi-parity graphs. Graphs and Combinatorics 5, 83–85 (1989). https://doi.org/10.1007/BF01788660
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DOI: https://doi.org/10.1007/BF01788660