Applications, Advantages and Disadvantages of Linked List

A Linked List is a linear data structure that is used to store a collection of data with the help of nodes. Please remember the following points before moving forward.

• The consecutive elements are connected by pointers / references.
• The last node of the linked list points to null.
• The entry point of a linked list is known as the head. 
• The common variations of linked lists are Singly, Doubly, Singly Circular and Doubly Circular.

Advantages of Linked Lists (or Most Common Use Cases):

• Linked Lists are mostly used because of their effective insertion and deletion.  We only need to change few pointers (or references) to insert (or delete) an item in the middle
• Insertion and deletion at any point in a linked list take O(1) time. Whereas in an array data structure, insertion / deletion in the middle takes O(n) time.
• This data structure is simple and can be also used to implement a stack, queues, and other abstract data structures.
• Implementation of Queue and Deque data structures : Simple array implementation is not efficient at all. We must use circular array to efficiently implement which is complex. But with linked list, it is easy and straightforward. That is why most of the language libraries use Linked List internally to implement these data structures..
• Linked List might turn out to be more space efficient compare to arrays in cases where we cannot guess the number of elements in advance. In case of arrays, the whole memory for items is allocated together. Even with dynamic sized arrays like vector in C++ or list in Python or ArrayList in Java. the internal working involves de-allocation of whole memory and allocation of a bigger chunk when insertions happen beyond the current capacity.

Applications of Linked Lists:

• Linked Lists can be used to implement stacks, queue, deque, sparse matrices and adjacency list representation of graphs.
• Dynamic memory allocation in operating systems and compilers (linked list of free blocks).
• Manipulation of polynomials
• Arithmetic operations on long integers.
• In operating systems, they can be used in Memory management, process scheduling (for example circular linked list for round robin scheduling) and file system.
• Algorithms that need to frequently insert or delete items from large collections of data.
• LRU cache, which uses a doubly linked list to keep track of the most recently used items in a cache.

Applications of Linked Lists in real world: 

• The list of songs in the music player are linked to the previous and next songs. 
• In a web browser, previous and next web page URLs can be linked through the previous and next buttons (Doubly Linked List)
• In image viewer, the previous and next images can be linked with the help of the previous and next buttons (Doubly Linked List)
• Circular Linked Lists can be used to implement things in round manner where we go to every element one by one.
• Linked List are preferred over arrays for implementations of Queue and Deque data structures because of fast deletions (or insertions) from the front of the linked lists.

Disadvantages of Linked Lists:

Linked lists are a popular data structure in computer science, but like any other data structure, they have certain disadvantages as well. Some of the key disadvantages of linked lists are:

• Slow Access Time: Accessing elements in a linked list can be slow, as you need to traverse the linked list to find the element you are looking for, which is an O(n) operation. This makes linked lists a poor choice for situations where you need to access elements quickly.
• Pointers or References: Linked lists use pointers or references to access the next node, which can make them more complex to understand and use compared to arrays. This complexity can make linked lists more difficult to debug and maintain.
• Higher overhead: Linked lists have a higher overhead compared to arrays, as each node in a linked list requires extra memory to store the reference to the next node.
• Cache Inefficiency: Linked lists are cache-inefficient because the memory is not contiguous. This means that when you traverse a linked list, you are not likely to get the data you need in the cache, leading to cache misses and slow performance.

In conclusion, linked lists are a powerful and flexible data structure, but they have certain disadvantages that need to be taken into consideration when deciding whether to use them or not. For example, if you need fast access time, arrays might be a better choice, but if you need to insert or delete elements frequently, linked lists might be the better choice.