Δ≥r-2的极大外平面图的4染色

Four Colourings of Maximum Outer Planar Graphs with Maximum Degree Δ ≥r-2

从最大度的角度讨论极大外平面图的染色．证明了以ｒ个顶点的圈Ｑｒ为标定界环的最大度Δ≥ｒ－２的任意两个极大外平面图都有公共４染色．

The four colourings of maximum outer planar graphs are studied in the view of maximum degree. It is proved that for any two maximum outer planar graphs with a common boundary circuit Q r and their maximum degree Δ ≥r-2 have common four colourings.