Published: 8 Dec 2025 | Reading Time: 8 min read
This comprehensive guide to linked lists in data structures covers:
Dynamic Data Structure Fundamentals: A linked list is a data structure that is dynamic where elements (nodes) are connected using pointers rather than stored contiguously like arrays.
Core Components: You learn the core components of a linked list in data structure: nodes, head, tail, and the role of pointers in memory management.
Types of Linked Lists: The blog explains all major types of linked lists: singly, doubly, circular, and sorted, along with advanced concepts like sentinel nodes and hash linking.
Operations and Complexity: It covers fundamental operations (insertion, deletion, traversal, searching, updating, reversal) plus their time & space complexities in detail.
Practical Implementation: You also get practical C code implementations, real-world applications, pros & cons, and a full comparison of linked lists vs arrays to help understand where linked lists excel and where they fall short.
Some data structures are fast. Some are flexible. But very few offer the perfect balance of freedom, adaptability, and simplicity the way a linked list does.
Arrays require space in advance. Memory blocks are still fixed. But a linked list? It extends when you extend. Decreases when you decrease. And it can be transferred with a certain ease that is almost indistinguishable from the world of static memory.
That's why the linked list in data structure is often the first true moment when learners realize: Data structures aren't just containers; they're systems with personality.
In this guide, we break down everything: types, operations, algorithms, implementation, and real-world uses, so you not only understand linked lists, but you think like them.
Linked lists in data structures refer to a linear data structure in which elements, called nodes, are stored separately in memory and connected through links. Instead of placing elements next to each other like arrays, each node holds its value and a link to the next node, forming a chain-like structure.
The list is traversed via a head pointer, which indicates the first node, and the chain is terminated when the link of a node points to null. Such a structure allows operations like insertions and deletions to be performed in an efficient manner since nodes can be added or removed without the need to shift other elements, thus linked lists are perfect for data that is volatile and changes often.
A node is the basic unit of a linked list in data structures. Each node typically contains two parts:
The head is a pointer or reference to the first node in the list. It's the starting point for traversing the list. If the list is empty, the head is set to null (or None in some languages).
The tail is the last node in the list. In a singly linked list, the tail's pointer is set to null, meaning there's no next node. In a circular linked list in data structure, the tail's pointer connects back to the head, forming a loop.
A null pointer is used to signal the end of the list. When a node's pointer is null, it means there are no more nodes to follow. This helps in stopping the traversal of the list at the right point.
Efficient memory management is a defining feature of linked lists, setting them apart from static data structures like arrays. At the heart of this flexibility are pointers (or references), which serve as the links connecting each node in the list.
In a linked list, each node contains two fields: one for storing data, and another for storing a pointer to the next node. This pointer holds the memory address (in languages like C/C++) or a reference (in languages like Java or Python) to the subsequent node, creating a chain of nodes that can be dynamically rearranged.
When a new node is added, memory is allocated for that node at runtime. The pointer in the previous node is updated to link to this new node, regardless of where the new node is located in memory. This means that, unlike arrays, the elements of a linked list do not need to be stored in consecutive memory locations.
struct Node {
int data;
struct Node* next;
};
struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
newNode->data = 10;
newNode->next = NULL;
In this example, newNode is dynamically allocated, and its next pointer can be set to link it into an existing list.
Linked list in data structures rely on dynamic memory allocation, meaning nodes are created as needed during program execution. Functions like malloc (in C/C++) or the new keyword (in Java, Python, etc.) are used to allocate space for each node. This method makes it possible for the list to expand or contract without requiring large contiguous memory blocks. Consequently, memory is consumed in an optimal way, and the list is capable of handling different amounts of data without being limited by an initial size.
The end of a linked list is marked by a null pointer, an explicit indication that there are no more nodes to traverse. In singly linked lists, the pointer of the last node is set to NULL (or None in Python), whereas in circular linked lists, the pointer of the last node points to the head, thus creating a continuous cycle.
Linked lists can store data internally (within each node) or externally (with each node holding a reference to data stored elsewhere). Internal storage is straightforward and efficient for small, fixed-size data. External storage becomes handy when nodes have to refer to large or shared data objects.
Pointers or references are the basis of linked list structures and memory management. They allow for dynamic allocation, flexible resizing, and efficient insertion and deletion by connecting nodes that are scattered in memory. Knowing how pointers function in linked lists is crucial for mastering dynamic data structures and memory management in software development.
Linked lists in data structures are linear structures that hold elements inside nodes, and each node is linked to the next by pointers. Depending on the way nodes are linked, linked lists are divided into several kinds. Each one of them has certain features that make it most efficient for a particular type of application.
A singly linked list in data structure is the most basic kind of linked list. Each node comprises:
The list is made of nodes, where each node is identified by the head pointer, and every node points to the next, thus creating a one-way chain. The pointer of the last node is assigned to NULL, indicating the end of the list.
It permits only forward traversal, thus the list can be iterated from head to tail, however, going backwards is not possible. Since each node has only one pointer, singly linked lists are less memory-consuming and are simple to put into practice.
Common uses: stacks, simple queues, and applications where only forward traversal is needed.
A doubly linked list extends the singly linked list by using two pointers in each node:
This bidirectional linking allows traversal in both forward and backward directions.
The added flexibility makes insertion and deletion (especially in the middle of the list) much easier, but the additional pointer increases memory usage.
Common uses: navigation systems, undo-redo functionality, playlist navigation, and applications requiring backward movement.
A circular linked list in data structure is a list that links the last node to the first node, thereby creating a loop. It may be either of the two types:
Circular linked lists enable the user to go through the data without being able to stop at a natural point. Since the end of the list is not marked with a NULL pointer, it is necessary to take special precautions to ensure that the traversal does not go on infinitely.
Common uses: round-robin scheduling, continuous playlists, buffer management, and systems that require repeated cyclic access.
A sorted linked list in data structure is one that preserves the nodes in a particular order, either ascending or descending, based on the data values. During an insertion of a new node, the node is inserted in the appropriate sorted position rather than just adding it at the start or the end.
Sorted lists may be structured as singly, doubly, or circular linked lists. Though they are valuable for holding ordered data, the insertion process takes longer as it is necessary to find the exact position for insertion.
Common uses: priority queues, ordered datasets, and real-time processing situations where elements have to be kept sorted.
Knowing these fundamental operations is a must for anyone intending to use linked lists in any way. Basically, the operations that can be performed on a linked list are:
Traversal means going through each node of the linked list, from the head to the last one. This procedure is required if one wants to print the list, work through each element, or carry out operations like searching or modifying values.
How it works:
Insertion is about including a new node into the list. Depending on the position where the new data is to be located, various methods of inserting a node can be applied.
Deletion removes a node from the linked list. Like insertion, deletion can occur at different positions:
Searching is to locate a node that holds the specified value. Usually, the list is traversed from head to tail, and the data of each node is compared with the target value. If there is a match, the search returns the node or its position; otherwise, it proceeds until the end of the list.
An update may refer to a change of the value in the data field of a node. The node is, most likely, obtained by a search. Changing data is an excellent mode of correction when data needs to be modified without changing the list's structure.
Reversal refers to changing a linked list's direction such that the last node is the head and all pointers are reversed. Generally, this is accomplished either by iterative or recursive methods, and it requires very accurate pointer operations to prevent losing the nodes.
Key steps for reversal:
These basic functions are the core of using linked lists, which allow dynamic storage, data manipulation of great flexibility, and the efficient handling of sequences that require insertions and deletions at a fast rate.
Working with a singly linked list in data structure involves managing nodes and pointers carefully. Below are the step-by-step algorithms for some of the most fundamental operations. These are written for singly linked lists, which contain data and a pointer to the next node.
Understanding how much time and space a linked list takes to perform an operation is very important when you want to decide if this data structure is efficient or not.
Skew Binary Random-Access List: Allows worst-case constant time for head/tail operations and worst-case logarithmic time for random access using a list of trees and the skew binary number system.
Understanding how to write a singly linked list in different programming languages is an absolute must for knowing how to use it in practice. Below is an example in C which performs basic operations like insertion, deletion, traversal, and search.
#include <stdio.h>
#include <stdlib.h>
struct Node {
int data;
struct Node* next;
};
// Create a new node
struct Node* createNode(int data) {
struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
newNode->data = data;
newNode->next = NULL;
return newNode;
}
// Insert at beginning
void insertAtBeginning(struct Node** head, int data) {
struct Node* newNode = createNode(data);
newNode->next = *head; // Link new node to old head
*head = newNode; // Move head to new node
}
// Insert at end
void insertAtEnd(struct Node** head, int data) {
struct Node* newNode = createNode(data);
// If list is empty
if (*head == NULL) {
*head = newNode;
return;
}
struct Node* temp = *head;
while (temp->next != NULL) {
temp = temp->next;
}
temp->next = newNode;
}
// Delete first node
void deleteAtBeginning(struct Node** head) {
if (*head == NULL) return;
struct Node* temp = *head;
*head = (*head)->next; // Move head to next node
free(temp); // Free old head
}
// Display the linked list
void displayList(struct Node* head) {
struct Node* temp = head;
while (temp != NULL) {
printf("%d -> ", temp->data);
temp = temp->next;
}
printf("NULL\n");
}
int main() {
struct Node* head = NULL;
insertAtEnd(&head, 10);
insertAtBeginning(&head, 20);
insertAtEnd(&head, 30);
displayList(head);
deleteAtBeginning(&head);
displayList(head);
return 0;
}
This code is building a singly linked list where each node consists of a number and a pointer to the next node. Initially, an empty list is made, then nodes are added at the end and at the beginning so the list becomes 20 -> 10 -> 30 -> NULL.
The displayList method goes through the list from the head to the tail and prints each element. The deleteAtBeginning function deletes the first node by changing the head pointer to the second node and releasing the old one, thus the list becomes 10 -> 30 -> NULL.
20 -> 10 -> 30 -> NULL
10 -> 30 -> NULL
Linked list in data structures are extensively used in real-world software systems as well as in theoretical models of computing due to their features like flexibility, efficient insertion/deletion operations, and dynamic memory utilization. These are the significant situations where linked lists are indispensable.
Linked lists manage free and used memory blocks in dynamic memory allocators and garbage collectors, enabling efficient allocation and deallocation of variable-sized memory.
Linked lists are the foundation for stack and queue data structures, allowing efficient insertion and deletion without shifting elements.
In hash tables that use chaining to resolve collisions, each bucket is implemented as a linked list, making it easy to add or remove entries.
Many text editors and graphic applications use doubly linked lists to store action history, enabling users to move backwards and forward through changes.
Browsers use doubly linked lists to manage the back and forward navigation history, allowing seamless movement between visited pages.
Playlists are typically done by means of linked lists, which allow for dynamically adding, deleting or changing the order of songs and videos in a simple way.
Circular linked lists are employed by operating systems to schedule processes or threads in a round-robin manner, thus giving each one equal access to resources.
Linked lists are employed in file systems for the management of directory entries, file allocation chains, and metadata blocks that are used for the efficient accessing and updating of the files.
Compilers and interpreters use linked lists to store and manage symbols, tokens, or intermediate representations due to their flexible insertion and deletion.
Linked lists help manage streams of data or serialized objects when the length is not fixed or known in advance.
Application of linked list are great for dynamic systems that change often, where flexible memory and efficient updates are more important than fast random access. The fact that they are found in operating systems, compilers, databases, browsers, and real-time applications tells us that they are very basic to modern computing.
A linked list is a data structure that is able to increase or decrease the size of the list while it is being executed, thus it is a perfect solution for those programs that have a variable number of elements.
If the position is known, a node can be added or deleted in O(1) time, without the need for shifting any other elements.
Memory is assigned on a per-node basis, thus there is no need for large contiguous memory blocks.
Stacks, queues, adjacency lists, polynomial lists, and graph structures can be implemented easily using linked lists.
Linked lists are more efficient than arrays in the case of frequent insertions, deletions, and rearrangements, especially if these operations are performed in the middle of the structure.
Elements cannot be accessed directly by index. Traversal from the head is required, which increases access time.
Each node requires extra memory to store one or more pointers, increasing storage usage.
The nodes that are stored in non-contiguous spaces of memory cause low cache performance during traversal.
To find an element, one has to spend O(n) time since nodes have to be visited sequentially until the searched one is found.
Converting singly linked list traversal to the backward direction is not easy and requires extra memory or modifications of the structure, thus certain operations become more complex.
| Feature | Arrays | Linked Lists |
|---|---|---|
| Memory Layout | Contiguous memory | Non-contiguous memory |
| Access Time | O(1) random access | O(n) sequential access |
| Insertion/Deletion | O(n) (shifting needed) | O(1) if node known |
| Memory Overhead | Low | High (extra pointers) |
| Cache Locality | Excellent | Poor |
| Resizing | Expensive (copy required) | Easy (dynamic) |
| Fragmentation Risk | Possible | Less likely |
| Best Use Case | Static datasets, frequent access | Dynamic datasets, frequent updates |
Linked list in data structures is one of the most important concepts of data structures, offering dynamic and adaptable methods of handling data. Knowing their kinds, operations, and applications is necessary for computer science students and software developers. Even though they have drawbacks such as no random access and additional memory overhead, their benefits in dynamic memory management and the simplicity of insertion/deletion make them still very useful in many situations.
One cannot go further with more complicated data structures and algorithms without first mastering linked lists, thereby improving one's problem-solving abilities and programming skills.
A linked list defines a linear data structure in which pointers are used to link its members, or nodes. Each node has data and a pointer to the next node, which allows for dynamic memory allocation.
Linked lists are different from arrays in a way that they do not need contiguous memory and can grow or shrink at runtime. Arrays access data faster, but linked lists are more efficient if there are a lot of insertions and deletions.
The primary types are singly linked lists, doubly linked lists, circular linked lists, and sorted linked lists. Each of them has different characteristics for different applications, such as forward/backward traversal or sorted insertion.
The set of operations consists of traversal, insertion, deletion, searching, and updating. These give users the ability to freely manipulate the nodes without having to shift elements as is necessary in the case of arrays.
Linked lists are used in music/video playlists, undo/redo features, memory management, and in implementing stacks, queues, and graph structures.
Pros include dynamic sizing and easy insertion/deletion. Cons are slower access (no indexing), extra memory for pointers, and less cache friendliness.
Linked lists can be implemented in almost any language, such as C, C++, Java, Python, and so on. The idea is the same, only the syntax and the way of memory being managed are different.
NxtWave
Source: NxtWave CCBP Blog - https://www.ccbp.in/blog/articles/linked-list-in-data-structure