AVL树:
https://mp.weixin.qq.com/s?__biz=Mzg2NzA4MTkxNQ==&mid=2247485220&idx=1&sn=7bca40ca5a3e703f6c9f89eb0f9f2be4&scene=21#wechat_redirect
红黑树:
https://cloud.tencent.com/developer/article/1447836