研究了3-可染色平面图的结构特征,利用discharging方法证明了不含4圈和5圈且三角形间的距离至少是2的平面图是3-可染色的.
By using the discharging method, it was proved that every planar graph is 3-colorable, provided that it has not any 4-, 5-cycles, and the distance between any two triangles is at least 2.