Abstract
We show that if G is a bipartite graph with no induced cycles on exactly 6 vertices, then the minimum number of chain subgraphs of G needed to cover E(G) equals the chromatic number of the complement of the square of line graph of G. Using this, we establish that for a chordal bipartite graph G, the minimum number of chain subgraphs of G needed to cover E(G) equals the size of a largest induced matching in G, and also that a minimum chain subgraph cover can be computed in polynomial time. The problems of computing a minimum chain cover and a largest induced matching are NP-hard for general bipartite graphs. Finally, we show that our results can be used to efficiently compute a minimum chain subgraph cover when the input is an interval bigraph.
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R. Sritharan is supported by a grant from the NSA.
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Abueida, A., Busch, A.H. & Sritharan, R. A Min–Max Property of Chordal Bipartite Graphs with Applications. Graphs and Combinatorics 26, 301–313 (2010). https://doi.org/10.1007/s00373-010-0922-0
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DOI: https://doi.org/10.1007/s00373-010-0922-0