七桥问题的并查集解法
https://blog.youkuaiyun.com/a664607530/article/details/60887449
https://www.cnblogs.com/joeylee97/p/6005488.html
图着色问题
https://blog.youkuaiyun.com/wang2332/article/details/79762379
https://blog.youkuaiyun.com/lovely_girl1126/article/details/77102559