https://www.cnblogs.com/suho/articles/8644154.html
https://www.cnblogs.com/minks/p/6228493.html
模块度modularity：https://blog.csdn.net/marywbrown/article/details/62059231
graph theory 图论
原文：https://www.cnblogs.com/oareii/p/10587045.html
