6/7/2023 0 Comments Enqueue vs dequeueQueue Enqueue FunctionĮnqueue is the insert functionality of the queue. All of these operations run in O(1) (constant) time. It may contain operations for returning the queue size, an "is empty" check, and an operation for returning (but not removing) the first element. The two main operations of a queue are Enqueue and Dequeue. ![]() This could be things such as incoming events and requests, or messages sent to a user. You should use a queue data structure whenever you want to handle items in a first in, first out ( FIFO) order. The person who was first in line is the first one to checkout. You can visualize this by thinking of standing in line at the grocery store. Regardless of when elements are inserted, the oldest element is removed first. ![]() What Is a Queue Data Structure?Ī Queue is a collection that keeps items in a sequence and abides by the first in, first out ( FIFO) rule. You can find the full implementation in my Github repository. If you don't care about any of the explanation, and are only looking for code snippets, that's cool too. While this implementation is based in C#, the code can be easily translated to Java as well. We will go over what it is, when you should use it, its basic operations, and the implementation. For all of these examples of how to implement data structures, I recommend you use what's provided in your language framework when available. We will be covering the queue data structure. If the internal array needs to be reallocated to accommodate the new element, this method becomes an O( n) operation, where n is Count.This post is a continuation of my series on data structures. If Count is less than the capacity of the internal array, this method is an O(1) operation. If Count already equals the capacity, the capacity of the Queue is increased by automatically reallocating the internal array, and the existing elements are copied to the new array before the new element is added. 'Contents of the second copy, with duplicates and nulls: ' This code example produces the following output: A queue can be enumerated without disturbing its contents.Ĭonsole.WriteLine("\nDequeuing '", _ The Contains method is used to show that the string "four" is in the first copy of the queue, after which the Clear method clears the copy and the Count property shows that the queue is empty. The Queue constructor is used again to create a second copy of the queue containing three null elements at the beginning. The elements of the copy are displayed.Īn array twice the size of the queue is created, and the CopyTo method is used to copy the array elements beginning at the middle of the array. The ToArray method is used to create an array and copy the queue elements to it, then the array is passed to the Queue constructor that takes IEnumerable, creating a copy of the queue. The Peek method is used to look at the next item in the queue, and then the Dequeue method is used to dequeue it. The Dequeue method is used to dequeue the first string. ![]() The elements of the queue are enumerated, which does not change the state of the queue. The code example creates a queue of strings with default capacity and uses the Enqueue method to queue five strings. The following code example demonstrates several methods of the Queue generic class, including the Enqueue method. The value can be null for reference types.
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