1.using五大用法：https://www.cnblogs.com/Joezzz/p/9927494.html
C++ bitset 常用函数及运算符: https://www.cnblogs.com/rabbithu/p/bitset.html
2.C++基本功和 Design Pattern系列 ctor & dtor：https://blog.csdn.net/yangdelong/article/details/1631500
3.Using-declaration： https://en.cppreference.com/w/cpp/language/using_declaration
