对于最大度为5的平面图,既有第一类,也有第二类.运用Discharge方法以及临界图的一些重要性质证明了:每个最大度为5且不含相交三角形的简单平面图的边色数等于5,即这样的平面图是第一类的.因此,给出了最大度为5的平面图分类的一个特征刻画.
Both class 1 and class 2 planar graph exist in planar graphs with △≤5 . It was proved that the chromatic index of every simple planar graph G with △= 5 and without intersecting triangles equaled to 5, i. e,such planar graphs were of class 1, where △ denoted the maximum degree of G.