https://blog.csdn.net/zhangyifei216/article/details/50545572
https://blog.csdn.net/fight_onlyfor_you/article/details/80317382
sin:https://blog.csdn.net/K346K346/article/details/48213811
c++ 输入输出
原文：https://www.cnblogs.com/lvmf/p/10946725.html
