5-桥图的色性

The Chromaticity of 5-bridge Graphs

由连接两个顶点的s条内部不交的路组成的图叫s-桥图,记作F(k1,k2,…,ks).本文给出了5-桥图F(3,a,b,c,d)(d≥c≥b≥a≥3)是色唯一的充分必要条件.

The graph consisting of s paths joining two vertices is called an s-bridge graph, denoted F（kI ,k2,… ,k,）. In this paper, we give a sufficient and necessary condition for 5-bridge graphs F（ 3,a,b,c,d） （ d≥ c≥ b ≥ a ≥ 3） to be chromatically unique.