Lecture 259:- Double Ended Queue DEQUEUE

In a double-ended queue (deque), the dequeue operation allows you to remove elements from both ends of the queue. In C++, you can use the std::deque container from the Standard Template Library (STL) to implement a double-ended queue.

Here's an example of how to use the std::deque to perform dequeue operations:

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#include <iostream> #include <deque> int main() {    std::deque<int> deque;    deque.push_back(10); // Enqueue at the back (rear) of the deque    deque.push_back(20);    deque.push_back(30);    deque.push_front(5); // Enqueue at the front (front) of the deque    deque.push_front(2);    std::cout << "Deque elements: ";    for (const auto& element : deque) {        std::cout << element << " ";    }    std::cout << std::endl;    deque.pop_back(); // Dequeue from the back (rear) of the deque    deque.pop_front(); // Dequeue from the front (front) of the deque    std::cout << "Deque elements after dequeue: ";    for (const auto& element : deque) {        std::cout << element << " ";    }    std::cout << std::endl;    return 0; }

In this example, we use the std::deque to create a double-ended queue named deque. We can use push_back() to enqueue elements at the back (rear) of the deque and push_front() to enqueue elements at the front (front) of the deque. The pop_back() operation dequeues an element from the back (rear) of the deque, and pop_front() dequeues an element from the front (front) of the deque.

The output of the program will be:

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Deque elements: 2 5 10 20 30 Deque elements after dequeue: 5 10 20

As you can see, elements are dequeued from both ends of the deque using the pop_back() and pop_front() operations. The std::deque is a versatile data structure that allows efficient insertion and deletion from both ends, making it suitable for implementing a double-ended queue.