科研之友
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摘要
An L(2, 1)-labeling of a graph G is a function f from the vertex set V(G) to the set of all nonnegative integers such that vertical bar f(x) - f(y)vertical bar >= 2 if d(x,y) = 1 and vertical bar f(x) - f(y)vertical bar >= 1 if d(x,y) = 2, where d(x,y) denotes the distance between x and y in G. The L(2, 1)-labeling number, lambda(G), of G is the smallest number k such that G has an L(2, 1)-labeling f with max{f(v) : v is an element of V(G)} = k. In this paper, we present a new characterization on d-disk graphs for d > 1. As an application, we give upper bounds on the L(2, 1)-labeling number for this classes of graphs.
- 出版日期2016-7
