STL QUEUE

STL QUEUE

• queues are a type of container adaptors.
• Operate in a FIFO context (first-in first-out), where elements are inserted into one end of the container and extracted from the other.
• queues are implemented as containers adaptors, which are classes that use an encapsulated object of a specific container class as its underlying container, providing a specific set of member functions to access it elements. Elements are pushed into the "back" of the specific container and popped from its "front".
• The underlying container may be one of the standard container class template or some other specifically designed container class. The only requirement is that it supports the following operations:

1. front()
2. back()
3. push_back()
4. pop_front()

• Therefore, the standard container class templates deque and list can be used. By default, if no container class is specified for a particular queue class, the standard container class template deque is used.

Example:

// queue::front
# include < iostream >
# include < queue >
using namespace std;

int main ()
{
  queue< int > myqueue;

  myqueue.push(77);
  myqueue.push(16);

  myqueue.front() -= myqueue.back();    // 77-16=61

  cout << "myqueue.front() is now " << myqueue.front() << endl;

  return 0;
}

Output:

myqueue.front() is now 61