Computer Science – 19.1 Algorithms | e-Consult

A queue can be implemented using a stack. The core idea is to utilize the stack's LIFO (Last-In, First-Out) property to simulate the FIFO (First-In, First-Out) behavior of a queue. The following operations on the stack are required:

• Enqueue: Adding an element to the rear of the queue. This is achieved by pushing the new element onto the stack. The time complexity of a push operation is O(1).
• Dequeue: Removing the element from the front of the queue. This is achieved by repeatedly popping elements from the stack until the stack is empty, and then pushing those elements back onto the stack in reverse order. The time complexity of popping is O(n) in the worst case (when all elements are on the stack).

Advantages:

• Simple Implementation: The implementation is relatively straightforward, leveraging the existing stack data structure.

Disadvantages:

• Inefficiency: The dequeue operation has a time complexity of O(n) in the worst case. This is because we need to pop all elements from the stack and then push them back onto the stack in the correct order. This makes the implementation less efficient than a queue implemented using a more appropriate data structure like a list or array.
• Space Overhead: The stack might require more space than a dedicated queue implementation, especially if the queue is expected to have a large number of elements.

In summary, while a stack can be used to implement a queue, it is generally not the most efficient approach due to the O(n) time complexity of the dequeue operation. Dedicated queue implementations are typically preferred for better performance.