In the field of data structures, a queue is a fundamental concept that represents a collection of elements with two primary operations: enqueue and dequeue. These operations allow elements to be inserted at the rear and removed from the front of the queue, respectively. Queues follow the FIFO (First-In-First-Out) principle, meaning that the element which is added first will be removed first.
Main Types of Queues:
1. Simple Queue:
A simple queue, also known as a linear queue, is the most basic type of queue.
It follows a simple rule where elements are inserted at one end and removed from the other end. This operation can be visualized as adding elements to one side and removing them from the opposite side.
2. Circular Queue:
In a circular queue, also referred to as a circular buffer, the last element points back to the first element instead of being null.
This structure enables better utilization of memory space by reusing vacant locations caused by dequeued elements. When enqueueing an element in a full circular queue, it wraps around to utilize empty spaces at the beginning.
3. Priority Queue:
A priority queue assigns a priority value to each element and allows removal based on their priorities.
Elements with higher priority values are dequeued before those with lower priority values. This type of queue can be implemented using various data structures such as arrays, linked lists, heaps, or binary search trees.
4. Double Ended Queue (Deque):
A double-ended queue or deque allows insertion and deletion at both ends (front and rear) in constant time.
This flexibility makes it useful for certain scenarios, such as implementing algorithms like breadth-first search (BFS) or simulation models. A deque can be visualized as a combination of a stack and a queue.
5. Circular Doubly Ended Queue:
A circular doubly ended queue is similar to both the circular queue and the double-ended queue.
It allows insertion and deletion at both ends, while also maintaining the circular property where the last element points back to the first element. This type of queue combines the advantages of both circular and double-ended queues.
In summary, queues are an essential concept in data structures that follow the FIFO principle. Different types of queues, including simple queues, circular queues, priority queues, double-ended queues, and circular doubly ended queues, serve various purposes in different scenarios. Understanding these types can help developers choose the appropriate queue implementation for their specific requirements.