Published: 5 May 2025 | Reading Time: 7 minutes
The linked list is one of the most important and frequently used concepts when learning data structures. In many real-world applications, linked lists are preferred over arrays because they provide dynamic memory allocation and effective insertion or deletion operations. In many of the systems we use daily, linked lists quietly enable everything from operating systems' memory management to text editors' data organization and queue or stack implementation.
This comprehensive guide explores the most useful and interesting applications of linked lists that every developer should be familiar with.
Linked lists come in different variations depending on how nodes are linked together. The three main types are Singly Linked Lists, Doubly Linked Lists, and Circular Linked Lists. Each type has its own advantages and use cases.
A Singly Linked List is the simplest type of linked list, where each node contains data and a pointer to the next node. The last node in the list points to NULL, indicating the end of the list.
A Doubly Linked List extends the singly linked list by adding an additional pointer in each node. Each node contains references to both the next and previous nodes, allowing traversal in both directions.
A Circular Linked List is a variation where the last node of the list is linked back to the first node, forming a loop. It can be implemented as a singly circular linked list (where the last node points to the first node) or a doubly circular linked list (where both ends are connected).
Linked lists offer several benefits over arrays, making them a preferred choice in scenarios where dynamic data handling is required.
Unlike arrays, which require a predefined size, linked lists are dynamically allocated. This means they can grow or shrink as needed, eliminating the need to reserve excess memory or reallocate when the capacity is exceeded.
In arrays, inserting or deleting an element often requires shifting multiple elements, which can be time-consuming. In contrast, linked lists only need to update pointers, making these operations more efficient, especially when modifying data in the middle or at the beginning of the list.
Linked lists allocate memory as needed for each node, reducing waste that occurs when pre-allocating large arrays. This is particularly useful in scenarios where the number of elements is unpredictable.
Despite their advantages, linked lists have some drawbacks compared to arrays, particularly in terms of performance and memory overhead.
Unlike arrays, where elements can be accessed directly using an index, linked lists require sequential traversal from the head node to locate an element. This makes searching slower, especially for large datasets, as it requires O(n) time complexity in the worst case.
Each node in a linked list requires extra memory to store a pointer (or two in the case of doubly linked lists). This overhead can be significant, especially when storing small data elements. Arrays, in contrast, store only the data, making them more memory-efficient when pointer storage isn't necessary.
Managing pointers in linked lists introduces additional complexity. Tasks such as inserting, deleting, or reversing a linked list require careful pointer manipulation, increasing the risk of errors like memory leaks or dangling pointers if not handled properly.
While linked lists provide flexibility and efficient modifications, their performance trade-offs in random access and memory usage make them suitable only for specific use cases where dynamic memory allocation is a priority.
Linked lists play a crucial role in various fields of computer science and real-world applications due to their flexibility and dynamic memory allocation.
Linked lists are ideal for implementing stacks (LIFO - Last In, First Out) and queues (FIFO - First In, First Out) since they allow efficient insertion and deletion without requiring a predefined size, unlike arrays.
Graphs often use adjacency lists, which are implemented using linked lists. This approach saves memory compared to adjacency matrices, especially for sparse graphs where many connections are absent.
To resolve hash collisions, linked lists are used in separate chaining. Multiple elements with the same hash key are stored in a linked list, reducing collision issues and ensuring efficient retrieval.
In polynomial arithmetic, each term is stored as a node in a linked list, with pointers connecting terms in increasing or decreasing order of exponents. This allows for efficient addition, subtraction, and differentiation of polynomials.
When performing calculations on large numbers that exceed the storage capacity of standard data types, linked lists store each digit as a node, making it easier to perform operations like addition and multiplication.
Operating systems use linked lists for dynamic memory allocation, tracking free and allocated memory blocks efficiently. For example, the buddy system for memory allocation often relies on linked lists.
Web browsers store browsing history in a doubly linked list, allowing users to move forward and backwards seamlessly through visited web pages.
Music players often use circular linked lists, enabling seamless playback where the last song in the playlist links back to the first song, ensuring continuous looping.
Image viewers use doubly linked lists to facilitate next and previous navigation, enabling smooth transitions between images in a gallery.
The round-robin scheduling algorithm in operating systems uses circular linked lists to manage processes, ensuring that each process gets an equal time slice before moving to the next.
A circular linked list is a type of linked list where the last node points back to the first node, forming a loop. This structure is particularly useful in scenarios where continuous iteration is required without resetting pointers.
A doubly linked list has two pointers: one pointing to the next node and another pointing to the previous node. This bidirectional nature makes it suitable for applications requiring easy forward and backwards traversal.
A singly linked list is a basic form of linked list where each node contains a pointer to the next node but no reference to the previous one. This structure is simple and efficient for applications that require sequential data processing.
Arrays and linked lists are two fundamental data structures, each with unique advantages and trade-offs. Choosing between them depends on the specific requirements of memory allocation, data manipulation, and access speed.
| Feature | Arrays | Linked Lists |
|---|---|---|
| Memory Allocation | Contiguous memory allocation | Non-contiguous memory allocation |
| Size Management | Fixed size | Dynamic size |
| Insertion (beginning/middle) | Expensive (O(n), requires shifting) | Efficient (O(1) at head, O(n) for specific position) |
| Insertion (end) | Efficient if space available (O(1)) | Efficient (O(1) if tail pointer is maintained) |
| Deletion (beginning/middle) | Expensive (O(n), requires shifting) | Efficient (O(1) at head, O(n) for specific position) |
| Deletion (end) | Efficient if size is tracked (O(1)) | O(n) (sequential traversal needed) |
| Random Access | O(1) (direct indexing possible) | O(n) (must traverse nodes) |
| Searching for an element | O(n) (linear search) or O(log n) (binary search in sorted array) | O(n) (must traverse nodes) |
| Memory Overhead | Low (stores only data) | High (extra pointers needed) |
| Cache Performance | High (better locality) | Low (scattered memory locations) |
| Resizing | Requires reallocation (expensive) | Dynamically grows as needed |
| Implementation Complexity | Simple (built-in array handling in most languages) | More complex (pointer management required) |
| Best Used For | Applications requiring fast indexing and fixed-size storage | Applications requiring frequent insertions/deletions |
Linked lists are a fundamental data structure that offers dynamic memory allocation and efficient insertion and deletion operations. Unlike arrays, they do not require contiguous memory, making them ideal for applications where the size of data changes frequently.
However, linked lists have drawbacks, such as higher memory overhead due to pointers and slower random access compared to arrays. Different types of linked lists—singly, doubly, and circular—are used in various applications in data structures, from memory management to data storage.
Their flexibility makes them crucial for implementing stacks, queues, hash tables, and graph representations. While linked lists provide efficiency in modifying data, their sequential access nature limits their performance in certain use cases.
Linked lists are categorized into three types: singly linked lists (where each node points to the next), doubly linked lists (where each node has pointers to both the previous and next nodes), and circular linked lists (where the last node connects back to the first). Each type serves different purposes depending on traversal and modification requirements.
Unlike arrays, which use contiguous memory allocation, linked lists use non-contiguous memory with pointers connecting elements. This enables efficient insertions and deletions but results in slower random access since traversal is required to reach an element.
Linked lists allocate memory dynamically as needed, reducing memory wastage compared to arrays that require predefined sizes. This makes them ideal for applications like memory allocation in operating systems and managing data structures that change in size frequently.
The main disadvantages include increased memory usage due to pointers, slower search times as elements must be traversed sequentially, and complex pointer management, which can lead to errors such as memory leaks or dangling pointers.
Linked lists are used in various applications, including implementing stacks and queues, managing symbol tables in compilers, handling undo/redo operations in software, scheduling tasks in operating systems, and representing graphs efficiently using adjacency lists.
In a circular linked list, the last node points back to the first node instead of containing a NULL reference. This enables continuous traversal and is commonly used in applications like round-robin scheduling, multiplayer game turns, and real-time data streaming.
Linked lists should be used when frequent insertions and deletions are required, the dataset size is unpredictable, or memory is fragmented and cannot be allocated contiguously. Arrays are preferable when fast indexing and cache performance are critical.
Source: NxtWave (CCBP.in)
Original URL: https://www.ccbp.in/blog/articles/application-of-linked-list