Queue Data Structure - GeeksforGeeks (2024)

Last Updated : 11 May, 2024

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What is Queue in Data Structures?

A queue is a linear data structure that follows the First-In-First-Out (FIFO) principle. It operates like a line where elements are added at one end (rear) and removed from the other end (front).

Basic Operations of Queue Data Structure

Enqueue (Insert): Adds an element to the rear of the queue.
Dequeue (Delete): Removes and returns the element from the front of the queue.
Peek: Returns the element at the front of the queue without removing it.
Empty: Checks if the queue is empty.
Full: Checks if the queue is full.

Applications of Queue

Task scheduling in operating systems
Data transfer in network communication
Simulation of real-world systems (e.g., waiting lines)
Priority queues for event processing queues for event processing

Implementation of Queues

Queues can be implemented using Two techniques:

Implementations of Queue Data Structure using Arrays
Implementations of Queue Data Structure using Linked List

Basics of Queue Data Structure

Introduction to Queue – Data Structure and Algorithm Tutorials
Basic Operations of Queue Data Structure
Different Types of Queue
Applications, Advantages and Disadvantages of Queue

Implementations of Queue in various Programming Languages

Queue in C++ Standard Template Library (STL)
Queue Interface In Java
Queue In Python
Queue In C#
Queue in Javascript

Other Implementations of Queue Data Structure

Implementation of Deque using doubly linked list
Implement a stack using single queue
Implement Queue using Stacks
How to efficiently implement k Queues in a single array?
LRU Cache Implementation

Easy Problems on Queue Data Structure

Implement Stack using Queues
Detect cycle in an undirected graph using BFS
Breadth First Search or BFS for a Graph
Traversing directory in Java using BFS
Vertical order traversal of Binary Tree using Map
Print Right View of a Binary Tree
Find Minimum Depth of a Binary Tree
Check whether a given graph is Bipartite or not

Medium Problems on Queue Data Structure

Flatten a multilevel linked list
Level with maximum number of nodes
Find if there is a path between two vertices in a directed graph
Print all nodes between two given levels in Binary Tree
Find next right node of a given key
Minimum steps to reach target by a Knight
Islands in a graph using BFS
Level order traversal line by line | Set 3 (Using One Queue)
Find the first non-repeating character from a stream of characters

Hard Problems on Queue Data Structure

Sliding Window Maximum (Maximum of all subarrays of size K)
Flood Fill Algorithm
Minimum time required to rot all oranges
Shortest path in a Binary Maze
An Interesting Method to Generate Binary Numbers from 1 to n
Maximum cost path from source node to destination
Shortest distance between two cells in a matrix or grid
Snake and Ladder Problem
Find shortest safe route in a path with landmines
Count all possible walks from a source to a destination with exactly K edges
Minimum Cost of Simple Path between two nodes in a directed and weighted graph
Minimum Cost Path in a directed graph via given set of intermediate nodes
Find the first circular tour that visits all petrol pumps

Quick Links:

‘Practice Problems’ on Queue
‘Videos’ on Queue
‘Quizzes’ on Queue

Recommended:

Learn Data Structure and Algorithms | DSA Tutorial
Queue in Go Language
Queue in Scala

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