Applications, Advantages and Disadvantages of Queue Last Updated : 01 Mar, 2024 Comments Improve Suggest changes Like Article Like Report A Queue is a linear data structure. This data structure follows a particular order in which the operations are performed. The order is First In First Out (FIFO). It means that the element that is inserted first in the queue will come out first and the element that is inserted last will come out last. It is an ordered list in which insertion of an element is done from one end which is known as the rear end and deletion of an element is done from the other which is known as the front end. Similar to stacks, multiple operations can be performed on the queue. When an element is inserted in a queue, then the operation is known as Enqueue and when an element is deleted from the queue, then the operation is known as Dequeue. It is important to know that we cannot insert an element if the size of the queue is full and cannot delete an element when the queue itself is empty. If we try to insert an element even after the queue is full, then such a condition is known as overflow whereas, if we try to delete an element even after the queue is empty then such a condition is known as underflow. Primary Queue Operations: void enqueue(int Element): When this operation is performed, an element is inserted in the queue at the end i.e. at the rear end. (Where T is Generic i.e we can define Queue of any type of data structure.) This operation take constant time i.e O(1).int dequeue(): When this operation is performed, an element is removed from the front end and is returned. This operation take constant time i.e O(1).Auxiliary Queue Operations: int front(): This operation will return the element at the front without removing it and it take O(1) time.int rear(): This operation will return the element at the rear without removing it, Its Time Complexity is O(1).int isEmpty(): This operation indicates whether the queue is empty or not. This Operation also done in O(1).int size(): This operation will return the size of the queue i.e. the total number of elements present in the queue and it's time complexity is O(1). Types of Queues: Simple Queue: Simple queue also known as a linear queue is the most basic version of a queue. Here, insertion of an element i.e. the Enqueue operation takes place at the rear end and removal of an element i.e. the Dequeue operation takes place at the front end.Circular Queue: This is mainly an efficient array implementation of Simple Queue. In a circular queue, the element of the queue act as a circular ring. The working of a circular queue is similar to the linear queue except for the fact that the last element is connected to the first element. Its advantage is that the memory is utilized in a better way. This is because if there is an empty space i.e. if no element is present at a certain position in the queue, then an element can be easily added at that position.Priority Queue: This queue is a special type of queue. Its specialty is that it arranges the elements in a queue based on some priority. The priority can be something where the element with the highest value has the priority so it creates a queue with decreasing order of values. The priority can also be such that the element with the lowest value gets the highest priority so in turn it creates a queue with increasing order of values.Dequeue: Dequeue is also known as Double Ended Queue. As the name suggests double ended, it means that an element can be inserted or removed from both the ends of the queue unlike the other queues in which it can be done only from one end. Because of this property it may not obey the First In First Out property. Implementation of Queue: Sequential allocation: A queue can be implemented using an array. It can organize a limited number of elements.Linked list allocation: A queue can be implemented using a linked list. It can organize an unlimited number of elements.Applications of Queue: Multi programming: Multi programming means when multiple programs are running in the main memory. It is essential to organize these multiple programs and these multiple programs are organized as queues. Network: In a network, a queue is used in devices such as a router or a switch. another application of a queue is a mail queue which is a directory that stores data and controls files for mail messages.Job Scheduling: The computer has a task to execute a particular number of jobs that are scheduled to be executed one after another. These jobs are assigned to the processor one by one which is organized using a queue.Shared resources: Queues are used as waiting lists for a single shared resource.Real-time application of Queue: Working as a buffer between a slow and a fast device. For example keyboard and CPU, and two devices on network.ATM Booth LineTicket Counter LineCPU task schedulingWaiting time of each customer at call centers.Advantages of Queue: A large amount of data can be managed efficiently with ease.Operations such as insertion and deletion can be performed with ease as it follows the first in first out rule.Queues are useful when a particular service is used by multiple consumers.Queues are fast in speed for data inter-process communication.Queues can be used in the implementation of other data structures.Disadvantages of Queue: The operations such as insertion and deletion of elements from the middle are time consuming.In a classical queue, a new element can only be inserted when the existing elements are deleted from the queue.Searching an element takes O(N) time.Maximum size of a queue must be defined prior in case of array implementation. Comment More infoAdvertise with us Next Article Different Types of Queues and its Applications S shreyasnaphad Follow Improve Article Tags : Queue DSA Practice Tags : Queue Similar Reads Queue Data Structure A Queue Data Structure is a fundamental concept in computer science used for storing and managing data in a specific order. It follows the principle of "First in, First out" (FIFO), where the first element added to the queue is the first one to be removed. It is used as a buffer in computer systems 2 min read Introduction to Queue Data Structure Queue is a linear data structure that follows FIFO (First In First Out) Principle, so the first element inserted is the first to be popped out. FIFO Principle in Queue:FIFO Principle states that the first element added to the Queue will be the first one to be removed or processed. So, Queue is like 5 min read Introduction and Array Implementation of Queue Similar to Stack, Queue is a linear data structure that follows a particular order in which the operations are performed for storing data. The order is First In First Out (FIFO). One can imagine a queue as a line of people waiting to receive something in sequential order which starts from the beginn 2 min read Queue - Linked List Implementation In this article, the Linked List implementation of the queue data structure is discussed and implemented. Print '-1' if the queue is empty.Approach: To solve the problem follow the below idea:we maintain two pointers, front and rear. The front points to the first item of the queue and rear points to 8 min read Applications, Advantages and Disadvantages of Queue A Queue is a linear data structure. This data structure follows a particular order in which the operations are performed. The order is First In First Out (FIFO). It means that the element that is inserted first in the queue will come out first and the element that is inserted last will come out last 5 min read Different Types of Queues and its Applications Introduction : A Queue is a linear structure that follows a particular order in which the operations are performed. The order is First In First Out (FIFO). A good example of a queue is any queue of consumers for a resource where the consumer that came first is served first. In this article, the diff 8 min read Queue implementation in different languagesQueue in C++ STLIn C++, queue container follows the FIFO (First In First Out) order of insertion and deletion. According to it, the elements that are inserted first should be removed first. This is possible by inserting elements at one end (called back) and deleting them from the other end (called front) of the dat 4 min read Queue Interface In JavaThe Queue Interface is a part of java.util package and extends the Collection interface. It stores and processes the data in order means elements are inserted at the end and removed from the front. Key Features:Most implementations, like PriorityQueue, do not allow null elements.Implementation Class 12 min read Queue in PythonLike a stack, the queue is a linear data structure that stores items in a First In First Out (FIFO) manner. With a queue, the least recently added item is removed first. A good example of a queue is any queue of consumers for a resource where the consumer that came first is served first. Operations 6 min read C# Queue with ExamplesA Queue in C# is a collection that follows the First-In-First-Out (FIFO) principle which means elements are processed in the same order they are added. It is a part of the System.Collections namespace for non-generic queues and System.Collections.Generic namespace for generic queues.Key Features:FIF 6 min read Implementation of Queue in JavascriptA Queue is a linear data structure that follows the FIFO (First In, First Out) principle. Elements are inserted at the rear and removed from the front.Queue Operationsenqueue(item) - Adds an element to the end of the queue.dequeue() - Removes and returns the first element from the queue.peek() - Ret 7 min read Queue in Go LanguageA queue is a linear structure that follows a particular order in which the operations are performed. The order is First In First Out (FIFO). Now if you are familiar with other programming languages like C++, Java, and Python then there are inbuilt queue libraries that can be used for the implementat 4 min read Queue in ScalaA queue is a first-in, first-out (FIFO) data structure. Scala offers both an immutable queue and a mutable queue. A mutable queue can be updated or extended in place. It means one can change, add, or remove elements of a queue as a side effect. Immutable queue, by contrast, never change. In Scala, Q 3 min read Some question related to Queue implementationImplementation of Deque using doubly linked listA Deque (Double-Ended Queue) is a data structure that allows adding and removing elements from both the front and rear ends. Using a doubly linked list to implement a deque makes these operations very efficient, as each node in the list has pointers to both the previous and next nodes. This means we 9 min read Queue using StacksGiven a stack that supports push and pop operations, your task is to implement a queue using one or more instances of that stack along with its operations.Table of ContentBy Making Enqueue Operation CostlyBy Making Dequeue Operation Costly Queue Implementation Using One Stack and RecursionBy Making 11 min read implement k Queues in a single arrayGiven an array of size n, the task is to implement k queues using the array.enqueue(qn, x) : Adds the element x into the queue number qn dequeue(qn, x) : Removes the front element from queue number qn isFull(qn) : Checks if the queue number qn is fullisEmpty(qn) : Checks if the queue number qn is em 15+ min read LRU Cache - Complete TutorialWhat is LRU Cache? Cache replacement algorithms are efficiently designed to replace the cache when the space is full. The Least Recently Used (LRU) is one of those algorithms. As the name suggests when the cache memory is full, LRU picks the data that is least recently used and removes it in order t 8 min read Easy problems on QueueDetect cycle in an undirected graph using BFSGiven an undirected graph, the task is to determine if cycle is present in it or not.Examples:Input: V = 5, edges[][] = [[0, 1], [0, 2], [0, 3], [1, 2], [3, 4]]Undirected Graph with 5 NodeOutput: trueExplanation: The diagram clearly shows a cycle 0 → 2 → 1 → 0.Input: V = 4, edges[][] = [[0, 1], [1, 6 min read Breadth First Search or BFS for a GraphGiven a undirected graph represented by an adjacency list adj, where each adj[i] represents the list of vertices connected to vertex i. Perform a Breadth First Search (BFS) traversal starting from vertex 0, visiting vertices from left to right according to the adjacency list, and return a list conta 15+ min read Traversing directory in Java using BFSGiven a directory, print all files and folders present in directory tree rooted with given directory. We can iteratively traverse directory in BFS using below steps. We create an empty queue and we first enqueue given directory path. We run a loop while queue is not empty. We dequeue an item from qu 2 min read Vertical Traversal of a Binary TreeGiven a Binary Tree, the task is to find its vertical traversal starting from the leftmost level to the rightmost level. If multiple nodes pass through a vertical line, they should be printed as they appear in the level order traversal of the tree.Examples: Input:Output: [[4], [2], [1, 5, 6], [3, 8] 10 min read Print Right View of a Binary TreeGiven a Binary Tree, the task is to print the Right view of it. The right view of a Binary Tree is a set of rightmost nodes for every level.Examples: Example 1: The Green colored nodes (1, 3, 5) represents the Right view in the below Binary tree. Example 2: The Green colored nodes (1, 3, 4, 5) repre 15+ min read Find Minimum Depth of a Binary TreeGiven a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. For example, minimum depth of below Binary Tree is 2. Note that the path must end on a leaf node. For example, the minimum depth of below Bi 15 min read Check whether a given graph is Bipartite or notGiven a graph with V vertices numbered from 0 to V-1 and a list of edges, determine whether the graph is bipartite or not.Note: A bipartite graph is a type of graph where the set of vertices can be divided into two disjoint sets, say U and V, such that every edge connects a vertex in U to a vertex i 8 min read Intermediate problems on QueueFlatten a multilevel linked list using level order traversalGiven a linked list where in addition to the next pointer, each node has a child pointer, which may or may not point to a separate list. These child lists may have one or more children of their own to produce a multilevel linked list. Given the head of the first level of the list. The task is to fla 9 min read Level with maximum number of nodesGiven a binary tree, the task is to find the level in a binary tree that has the maximum number of nodes. Note: The root is at level 0.Examples: Input: Binary Tree Output : 2Explanation: Input: Binary tree Output:1Explanation Using Breadth First Search - O(n) time and O(n) spaceThe idea is to traver 12 min read Find if there is a path between two vertices in a directed graphGiven a Directed Graph and two vertices src and dest, check whether there is a path from src to dest.Example: Consider the following Graph: adj[][] = [ [], [0, 2], [0, 3], [], [2] ]Input : src = 1, dest = 3Output: YesExplanation: There is a path from 1 to 3, 1 -> 2 -> 3Input : src = 0, dest = 11 min read All nodes between two given levels in Binary TreeGiven a binary tree, the task is to print all nodes between two given levels in a binary tree. Print the nodes level-wise, i.e., the nodes for any level should be printed from left to right. Note: The levels are 1-indexed, i.e., root node is at level 1.Example: Input: Binary tree, l = 2, h = 3Output 8 min read Find next right node of a given keyGiven a Binary tree and a key in the binary tree, find the node right to the given key. If there is no node on right side, then return NULL. Expected time complexity is O(n) where n is the number of nodes in the given binary tree.Example:Input: root = [10 2 6 8 4 N 5] and key = 2Output: 6Explanation 15+ min read Minimum steps to reach target by a Knight | Set 1Given a square chessboard of n x n size, the position of the Knight and the position of a target are given. We need to find out the minimum steps a Knight will take to reach the target position.Examples: Input: KnightknightPosition: (1, 3) , targetPosition: (5, 0)Output: 3Explanation: In above diagr 9 min read Islands in a graph using BFSGiven an n x m grid of 'W' (Water) and 'L' (Land), the task is to count the number of islands. An island is a group of adjacent 'L' cells connected horizontally, vertically, or diagonally, and it is surrounded by water or the grid boundary. The goal is to determine how many distinct islands exist in 15+ min read Level order traversal line by line (Using One Queue)Given a Binary Tree, the task is to print the nodes level-wise, each level on a new line.Example:Input:Output:12 34 5Table of Content[Expected Approach – 1] Using Queue with delimiter – O(n) Time and O(n) Space[Expected Approach – 2] Using Queue without delimiter – O(n) Time and O(n) Space[Expected 12 min read First non-repeating character in a streamGiven an input stream s consisting solely of lowercase letters, you are required to identify which character has appeared only once in the stream up to each point. If there are multiple characters that have appeared only once, return the one that first appeared. If no character has appeared only onc 15+ min read Like