On the Structure of Graphs with Non-Surjective L(2, 1)-Labelings

نویسندگان

  • John P. Georges
  • David W. Mauro
چکیده

For a graph G, an L(2, 1)-labeling of G with span k is a mapping L → {0, 1, 2, . . . , k} such that adjacent vertices are assigned integers which differ by at least 2, vertices at distance two are assigned integers which differ by at least 1, and the image of L includes 0 and k. The minimum span over all L(2, 1)-labelings of G is denoted λ(G), and each L(2, 1)-labeling with span λ(G) is called a λ-labeling. For h ∈ {1, . . . , k − 1}, h is a hole of L if and only if h is not in the image of L. The minimum number of holes over all λ-labelings is denoted ρ(G), and the minimum k for which there exists a surjective L(2, 1)-labeling onto {0, 1, . . . , k} is denoted μ(G). This paper extends the work of Fishburn and Roberts on ρ and μ through the investigation of an equivalence relation on the set of λ-labelings with ρ holes. In particular, we establish that ρ ≤ Δ. We analyze the structure of those graphs for which ρ ∈ {Δ−1,Δ}, and we show that μ = λ+1 whenever λ is less than the order of the graph. Finally, we give constructions of connected graphs with ρ = Δ and order t(Δ + 1), 1 ≤ t ≤ Δ.

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عنوان ژورنال:
  • SIAM J. Discrete Math.

دوره 19  شماره 

صفحات  -

تاریخ انتشار 2005