【摘 要】
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A graph is 1-planar if it can be drawn on the Euclidean plane so that each edge is crossed by at most one other edge.A proper vertex k-coloring of a graph G is defined as a vertex coloring from a set of k colors such that no two adjacent vertices have the
【机 构】
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Department of Mathematics and Statistics,Shandong Normal University,Jinan 250358,China
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A graph is 1-planar if it can be drawn on the Euclidean plane so that each edge is crossed by at most one other edge.A proper vertex k-coloring of a graph G is defined as a vertex coloring from a set of k colors such that no two adjacent vertices have the same color.A graph that can be assigned a proper k-coloring is k-colorable.A cycle is a path of edges and vertices wherein a vertex is reachable from itself.A cycle contains k vertices and k edges is a k-cycle.In this paper,it is proved that 1-planar graphs without 4-cycles or 5-cycles are 5-colorable.
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