Implementing a Queue
Explore how to implement a queue data structure in C++ using both array-based and linked list-based methods. Understand their memory layouts, operational differences, advantages, and limitations to develop efficient queue implementations suitable for various scenarios and improve your C++ coding skills.
Now that we understand what a queue is, the next step is to examine how it is implemented. A queue is an abstract data structure. It defines a set of behaviors, but it does not dictate how the data must be stored or managed in memory. Just like a stack, a queue can be built on top of different underlying structures, using both an array and a linked list.
Using an array
In an array-based implementation, we use an array, or a dynamic array, to store queue elements, with all elements stored in a contiguous block of memory. The queue elements are placed in the array, and array indices represent the front and rear of the queue. A size counter tracks the number of elements currently in the queue.
If the array has a fixed size, then the queue has a maximum capacity. If a dynamic array is used, the structure can grow, although some queue designs still manage front and rear positions explicitly.
Here is what an array-based queue looks like:
As elements are dequeued from the front, the positions they occupied become empty. In a naive implementation, this can waste space. More advanced implementations use a “circular queue” technique to reuse these empty positions, which we will explore later.
Implementation in C++
We implement an array-based queue using a class that contains the following elements: the capacity (maximum number of elements the queue can hold), the underlying array data, ...