How to use std:: in c++

std is the namespace in C that contains standard library components. In order to use std, use the "using namespace std;" statement. Using symbols directly from the std namespace can simplify your code, but is recommended only when needed to avoid namespace pollution.

std usage in C

In C, std is a name Space, which contains all standard functions, classes and objects of the C standard library. All standard library components are accessible by using the std namespace.

How to use std

In order to use the std namespace, you need to use the using namespace std; statement in the code. This statement instructs the compiler to automatically search for symbols in the std namespace when parsing code.

using namespace std;

After using the using namespace std; statement, you can directly use the symbols in the std namespace without using std:: prefix. For example:

// 使用 std::cout 输出"Hello, World!"
cout << "Hello, World!" << endl;

Common components in the std namespace

The following are some commonly used components in the std namespace:

• I/O streams: cin, cout, endl
• Containers: vector, map, set
• Algorithm: find, sort, reverse
• ##Iterator: vector::iterator
• Exception : exception, bad_alloc, out_of_range

## Avoid using std::

Although using the

using namespace std;

statement can simplify the code, it may cause namespace pollution. Therefore, it is recommended to use the using namespace std; statement only when needed. For example, you can use using namespace std; within a specific function or block of code, rather than throughout your entire program.

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