A Class of Graphs of f-Class 1

  • Authors:
  • Xia Zhang;Guizhen Liu

  • Affiliations:
  • School of Mathematics and System Science, Shandong University, 250100, P.R. China;School of Mathematics and System Science, Shandong University, 250100, P.R. China

  • Venue:
  • ICCS '07 Proceedings of the 7th international conference on Computational Science, Part III: ICCS 2007
  • Year:
  • 2007

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Abstract

An f-coloring of a graph G is an edge-coloring of G such that each color appears at each vertex v 驴 V(G) at most f(v) times. The minimum number of colors needed to f-color G is called the f-chromatic index of G, and denoted by 驴驴 f (G). Any simple graph G has f-chromatic index equal to Δ f (G) or Δ f (G) + 1, where $\Delta_{f}(G)=\max_{v\in V(G)}\{\lceil\frac{d(v)}{f(v)}\rceil\}$. If 驴驴 f (G) = Δ f (G), then G is of f-class 1; otherwise G is of f-class 2. In this paper, we show that if f(v) is positive and even for all $v\in V_0^*(G)\cup N_G(V_0^*(G))$, then G is of f-class 1, where $V^{*}_{0}(G)=\{v\in V(G):\frac{d(v)}{f(v)}=\Delta_{f}(G)\}$ and $N_G(V_0^*(G))=\{v\in V(G):uv\in E(G), u\in V_0^*(G)\}$. This result improves the simple graph version of a result of Hakimi and Kariv [4].