直接看代码吧

#include <iostream>
#include <string>/*
A string is actually an object of the C++ Standard Library class string. 
This class is defined in header <string>, and the name string, like cout, belongs to namespace std.
To enable string-relative-statement compile, includes the <string> header.
The using directive in "using namespace std;" allows us to simply write string rather than std::string.
For now, you can think of string variables like variables of other types such as int.The class template basic_string provides typical string-manipulation operations such as
copying, searching, etc.
The template definition and all support facilities are defined in namespace std; 
these include the typedef statement "typedef basic_string< char > string;"that creates the alias type string
for basic_string<char>. To use strings, include header <string>.
*/using std::cout;
using std::cin;