add1

代码说明：

  编写一个完整的C++程序，分别用下面的三个函数，给在函数main中定义的变量count加上1，然后比较一下三种方法的优劣。三个函数是：(To write a complete C++ of procedures, with the following three functions, respectively, to the variable count defined in function main with a, then compare the pros and cons of the three methods. The three functions are:)