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On the number of unlabeled vertices in edge-friendly labelings of graphs. (English) Zbl 1232.05205
Summary: Let $$G$$ be a graph with vertex set $$V(G)$$ and edge set $$E(G)$$, and $$f$$ be a $$0 - 1$$ labeling of $$E(G)$$ so that the absolute difference in the number of edges labeled 1 and 0 is no more than one. Call such a labeling fedge-friendly. We say an edge-friendly labeling induces a partial vertex labeling if vertices which are incident to more edges labeled 1 than 0, are labeled 1, and vertices which are incident to more edges labeled 0 than 1, are labeled 0. Vertices that are incident to an equal number of edges of both labels we call unlabeled. Call a procedure on a labeled graph a label switching algorithm if it consists of pairwise switches of labels. Given an edge-friendly labeling of $$K_{n}$$, we show a label switching algorithm producing an edge-friendly relabeling of $$K_{n}$$ such that all the vertices are labeled. We call such a labeling opinionated.
##### MSC:
 05C78 Graph labelling (graceful graphs, bandwidth, etc.) 05C30 Enumeration in graph theory
##### Keywords:
partial vertex labeling
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