JOURNAL OF SHANDONG UNIVERSITY(NATURAL SCIENCE) ›› 2017, Vol. 52 ›› Issue (4): 34-39.doi: 10.6040/j.issn.1671-9352.0.2016.171

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Every 1-planar graph without cycles of length 3 or 4 is 5-colorable

WANG Ye, SUN Lei*   

  1. School of Mathematics and Statistics, Shandong Normal University, Jinan 250014, Shandong, China
  • Received:2016-04-18 Online:2017-04-20 Published:2017-04-11

Abstract: A graph G is called 1-planar graph if it can be drawn on the plane so that each edge is crossed by at most one other edge. A propervertexcoloring of G is an assignment φ of integer to the vertex of G such that φ(u)≠φ(v)if the vertex u and v adjacent in G. A k-coloring is a proper vertex coloring using k colors at least. The theorem that every 1-planar graph without cycles of length 3 or 4 is 5-colorable was given by the Discharging Method.

Key words: cross vertices, cross faces, k-colorable, 1-planar graph

CLC Number: 

  • O157.5
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