A short cycle means a cycle of length at most 7.In this paper,we prove that planar graphs without adjacent short cycles are 3-colorable.This improves a result of Borodin et al.(2005).
WANG YingQian 1,MAO XiangHua 1,LU HuaJing 2 & WANG WeiFan 1 1 College of Mathematics,Physics and Information Engineering,Zhejiang Normal University,Jinhua 321004,China
It is known that every triangle-free plane graph is 3-colorable.However,such a triangle-free plane graph may not be 3-choosable.In this paper,we prove that a triangle-free plane graph is 3-choosable if no 4-cycle in it is adjacent to a 4-or a 5-cycle.This improves some known results in this direction.
