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On the structure of bull-free perfect graphs

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Abstract

A bull is a graph obtained by adding a pendant vertex at two vertices of a triangle. Chvátal and Sbihi showed that the Strong Perfect Graph Conjecture holds for bull-free graphs. We show that bull-free perfect graphs are quasi-parity graphs, and that bull-free perfect graphs with no antihole are perfectly contractile. Our proof yields a polynomial algorithm for coloring bull-free strict quasi-parity graphs

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Partially supported by CNPq, grant 30 1160/91.0

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de Figueiredo, C.M.H., Maffray, F. & Porto, O. On the structure of bull-free perfect graphs. Graphs and Combinatorics 13, 31–55 (1997). https://doi.org/10.1007/BF01202235

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