Queue constructor
Syntax:
  #include <queue>
  queue();
  queue( const Container& con );

Queues have a default constructor as well as a copy constructor that will create a new queue out of the container con.

For example, the following code creates a queue of strings, populates it with input from the user, and then displays it back to the user:

  queue<string> waiting_line;
 
while( waiting_line.size() < 5 ) {
    cout
<< "Welcome to the line, please enter your name: ";
   
string s;
    getline
( cin, s );
    waiting_line
.push(s);
 
}

 
while( !waiting_line.empty() ) {
    cout
<< "Now serving: " << waiting_line.front() << endl;
    waiting_line
.pop();
 
}

When run, the above code might produce this output:

  Welcome to the line, please enter your name: Nate
 
Welcome to the line, please enter your name: lizzy
 
Welcome to the line, please enter your name: Robert B. Parker
 
Welcome to the line, please enter your name: ralph
 
Welcome to the line, please enter your name: Matthew
 
Now serving: Nate
 
Now serving: lizzy
 
Now serving: Robert B. Parker
 
Now serving: ralph
 
Now serving: Matthew