This will continue as we enqueue more items. Next, we will see what happens as we enqueue more itemsĪ second item has been added but only the back moved. The position of the front and back have moved as well. We have inserted (enqueued) our first item – 5. Let us add some items into our array and see what happens. When both positions are at -1, it means the array is empty. The arrows show the position of the front and back of our array. This will enable us move the front and back position properly as values are added. While implementing our code, we are going to set the index of the front and back values of our array to -1. The indices of arrays in most programming languages start from 0. Display: Prints all the items in the queue.īefore we see how to implement this with code, you need to understand how the enqueue and dequeue operations work and how they affect the front and back positions.Front/ Peek: Returns the value of the item in front of the queue without dequeuing (removing) the item.Dequeue: Removes an item from the front of the queue.Enqueue: Adds an item from the back of the queue.The following operations are commonly used in a queue: Whichever structure you go with, always remember that insertion of items happens through the back and deletion through the front. Note that you can reverse the structure of your queue – you can have the front on the right and the back on the left side. There are terms used for the insertion and deletion of items in a queue which we will cover in the next section. The items are inserted through the back and removed through the front. The image shows an array with various cells. Here is a diagram to help you understand better: The back is where the items are inserted and the front is the part of the queue where items are removed/deleted. For the purpose of clarity and consistency, we will stick to using front and back. Structure of a QueueĪ queue is mainly made up of two parts: the front/head and the rear/tail/back. They are helped in the order which they came. Once one individual is attended to, they leave the queue for the next person to be attended to. Using a real world example, we can compare a queue data structure to a queue of individuals standing in line for a service. You can also say that items are removed in the order they were inserted. This implies that the first item to be inserted will be the first to be removed. What Is a Queue?Ī queue is linear data structure that consists of a collection is of items that follow a first-in-first-out sequence. Implementation 1: Using natural order of the elements.In this article, we will talk about the queue data structure, its operations, and how to implement these operations using an array in Java. Syntax: Comp_set = (PriorityQueue)Priority_parator()Ĭomparator method does not take any parameters. Priority queue comparator function is used to return the order of the elements that are stored in the priority queue Comparator method returns the null value if the queue follows the same order of the elements. If two elements are having the same priority then they are served according to their order in the queue.The element with highest priority first.In the priority queue, every element has priority assigned to it.In the priority queue, all the elements are arranged either in ascending order or descending order. The priority of the element determines the order in which elements are removed from the priority queue. Priority queue is an abstract data type, It is a type of queue in which each element has a priority assigned to it.
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