What Is Deque Data Structure?

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Angela Bailey

A deque, short for “double-ended queue,” is a linear data structure that allows insertion and deletion of elements from both ends. It can be thought of as a combination of a stack and a queue, as it supports both LIFO (Last-In-First-Out) and FIFO (First-In-First-Out) operations. In this article, we will explore what a deque is, how it works, and its various applications.

Operations on Deque

A deque typically supports the following operations:

• Insertion at Front: Adds an element to the front of the deque.
• Insertion at Rear: Adds an element to the rear of the deque.
• Deletion from Front: Removes an element from the front of the deque.
• Deletion from Rear: Removes an element from the rear of the deque.
• Accessing Front Element: Retrieves the element at the front of the deque without removing it.
• Accessing Rear Element: Retrieves the element at the rear of the deque without removing it.

Implementation

A deque can be implemented using various data structures such as arrays, linked lists, or doubly linked lists. Each implementation has its own advantages and trade-offs in terms of time complexity and space efficiency.

Array-based Implementation

In an array-based implementation, we can use a regular array and two pointers to keep track of the front and rear positions. Insertions and deletions can be performed by shifting elements to maintain continuity. However, this approach may have limitations on dynamic resizing if the array is fixed in size.

A linked list-based implementation uses nodes to store elements, and each node contains a reference to the next and previous nodes. This allows for efficient insertions and deletions at both ends of the deque. However, accessing elements at arbitrary positions may require traversing the list.

Applications of Deque

Deques have various applications in computer science and real-world scenarios. Some common use cases include:

• Dequeuing: Deques are commonly used as a double-ended queue for dequeuing elements efficiently from both ends.
• Sliding Window: Deques can be used to efficiently solve sliding window problems, where a window of fixed size moves through an array or sequence.
• Palindrome Checking: Deques can be utilized to check whether a given string or sequence is a palindrome by comparing characters from both ends.
• Scheduling Algorithms: Deques are useful in scheduling algorithms that involve managing tasks based on their priority or arrival time.

In conclusion, a deque is a versatile data structure that offers flexibility in managing elements from both ends. Its efficient operations make it suitable for various applications across different domains. By understanding how deques work and their potential use cases, you can enhance your problem-solving skills and improve the efficiency of your algorithms.