https://blog.csdn.net/yao_zou/article/details/50759301
https://blog.csdn.net/e5Max/article/details/50180905
https://www.cnblogs.com/dolphin0520/archive/2011/04/04/2005061.html
initializer_list：http://www.cppblog.com/liyiwen/archive/2009/07/26/91248.html
for_each: https://www.cnblogs.com/zhangkele/p/9373063.html
https://blog.csdn.net/asd1230123dsa/article/details/83793583
this指针：https://www.cnblogs.com/windsun/p/11323143.html
B站学习时间复杂度分析