中文说明：该代码是利用贪心算法思想求解着色问题，先去度最大的节点，开始着色，然后用同一颜色尽可能多的着色，直到无法给节点着色，就增加颜色，直到所有节点都着色，算法结束。
English Description：
The code is to use the idea of greedy algorithm to solve the coloring problem, first go to the node with the largest degree, start coloring, and then use the same color as much as possible, until the node can not be colored, increase the color, until all nodes are colored, the end of the algorithm.