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Linked List vs Array: Differences, Types, and Advantages

Updated on 17/03/2025508 Views

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Linked lists and arrays are two types of data structures used in almost every algorithm or system for different purposes. However, many of us are unaware of how these two data structures (Linked List vs Array) differ from each other. If you are also one of those people, don't worry. You’re in the right place. This article will discuss Linked List vs Array in great detail.

The main difference between a linked list and an array is that a linked list stores elements (nodes) in non-contiguous memory locations, where each node is allocated separately in memory, and nodes are connected through pointers. In contrast, an array stores elements in contiguous memory locations, meaning all elements are stored next to each other in a single block of memory.

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Now that we have some ideas related to linked list vs array, let’s explore other differences in a tabular format for a better understanding.

Linked List vs Array: Tabular Comparison

Here’s a quick tabular comparison between linked list vs array for a better understanding:

Aspect	Linked List	Array
Memory Allocation	Non-contiguous memory allocation (nodes are scattered in memory, linked by pointers).	Contiguous memory allocation (elements are stored next to each other).
Access Time	Slower access (O(n)), requires traversal from the head node.	Fast access (O(1)) using indices.
Insertion/Deletion	Efficient insertions and deletions (O(1)) at the beginning or middle (requires pointer manipulation). Traversal needed for insertion/deletion at arbitrary positions (O(n)).	Insertion and deletion are costly (O(n)), especially in the middle or at the beginning, due to the need to shift elements.
Fixed or Dynamic Size	Dynamic size; can grow or shrink as needed.	Fixed size; resizing requires reallocation (unless dynamic arrays are used).
Memory Efficiency	Less memory-efficient due to the overhead of pointers in each node.	More memory-efficient; no extra memory for pointers.
Resizing	Dynamic resizing (nodes are allocated as needed).	Fixed size; resizing an array is costly and requires reallocation.
Search Time (Unsorted)	O(n) for linear search through elements.	O(n) for linear search through elements.
Search Time (Sorted)	O(n) for linear search; no direct indexing.	O(log n) if using binary search (sorted array).
Cache Performance	Poor cache performance due to non-contiguous memory allocation.	Better cache performance due to contiguous memory allocation.
Best Use Case	Ideal for dynamic data where frequent insertions/deletions are needed, especially for data with unpredictable sizes.	Best when the number of elements is fixed or known, and fast, random access to elements is needed.
Implementation Complexity	More complex due to pointer management and dynamic memory allocation.	Simple to implement and manage.
Types	Singly Linked List, Doubly Linked List, Circular Linked List.	One-dimensional, multi-dimensional arrays (2D, 3D, etc.).
Space Complexity	O(n) for elements + O(n) for pointers (additional memory overhead for pointers).	O(n) for elements (no extra space overhead).

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What is a Linked List?

A Linked List is a linear data structure in which elements, called nodes, are stored in non-contiguous memory locations. Each node contains two parts: the data and a pointer (or reference) to the next node in the sequence.

Linked lists allow for dynamic memory allocation, making them more flexible than arrays. They are particularly useful for scenarios where elements need to be frequently inserted or removed from the middle of the collection.

Types of Linked List

There are mainly three types of linked list:

1. Singly Linked List

Each node contains data and a pointer to the next node in the list.
It is unidirectional. Traversal is done in one direction, from the head to the last node.
Operations such as insertion, deletion, and search are done sequentially.

2. Doubly Linked List

Each node contains data, a pointer to the next node, and a pointer to the previous node.
Allows for bidirectional traversal. You can traverse forward as well as backward, which in turn makes operations like deletion and insertion more flexible and efficient.

3. Circular Linked List

The last node points back to the first node, making the list circular.
It can be singly or doubly circular, but the key feature is the circular reference that loops back to the first node.

Advantages and Disadvantages of Linked List

Here are the advantages of linked list:

Dynamic size: Linked lists can grow and shrink as needed without predefining their size.
Efficient insertion/deletion: Insertions and deletions at the beginning, middle, or end of the list are faster (O(1)) compared to arrays, as no shifting of elements is required.
Flexible memory usage: Memory is allocated as needed for each node, which makes linked lists more memory-efficient for large data sets.

Here are the disadvantages of linked list:

Sequential access: Accessing an element requires traversal from the head, resulting in slower access time (O(n)) compared to arrays.
Memory overhead: Each node requires extra memory for storing pointers in addition to the data.
Complex implementation: Linked lists are more complex to implement, especially when managing pointers during insertion, deletion, or traversal.

What is Array?

An Array is a collection of elements stored in contiguous memory locations. Each element is of the same data type and is accessible by its index.

Arrays allow for fast access to elements (O(1)) since the index directly corresponds to the element's memory location. Arrays are generally used when the number of elements is known in advance and when fast access to elements is required.

Types of Array

Arrays are classified mainly four types:

One-dimensional Array: A single list of elements. For example, an array of integers or strings.
Multi-dimensional Array: Arrays with more than one dimension. For example, a 2D array (matrix) where elements are accessed using two indices, like rows and columns.
Dynamic Array: An array that can resize automatically when elements are added or removed. This is usually implemented with arrays like ArrayList in Java or vector in C++.
Associative Array (Hash Array): Also known as a map or dictionary, where each element is accessed using a key instead of an index.

Want to explore arrays in-depth? If so, read What is an Array in Data Structures? Key Concepts, Types, and Operations article.

Advantages and Disadvantages of Array

Here are the advantages of array:

Fast access: Arrays allow for constant time access (O(1)) to elements using indices.
Simple structure: Arrays are simple to implement and understand.
Memory efficiency: Arrays do not require additional memory overhead for pointers, unlike linked lists.

Here are the disadvantages of array:

Fixed size: Once created, the size of an array is fixed. Resizing requires allocating a new array, which can be inefficient.
Costly insertions/deletions: Inserting or deleting elements in the middle requires shifting the remaining elements, resulting in O(n) time complexity.
Contiguous memory: The need for contiguous memory blocks can be a problem in cases of large data sets or fragmented memory

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Linked List vs Array - Key Differences

Here are the key differences between Linked List vs Array:

In a linked list, memory is allocated non-contiguously, meaning each node is stored separately, and nodes are connected by pointers. Meanwhile, in an array, memory is allocated contiguously, meaning all elements are stored next to each other in a continuous block of memory.
In a linked list, accessing an element is slower (O(n)) because you must traverse the list from the head to the desired node. On the contrary, in an array, accessing an element is fast (O(1)) because each element can be accessed directly using its index.
The linked list size is dynamic, i.e., it can grow or shrink as needed. Nodes are added or removed without reallocating memory. On the other hand, the array size is fixed at the time of creation. If more elements are needed, the array must be resized, which involves creating a new array and copying the elements.
In a linked list, searching for an element in an unsorted list takes linear time (O(n)), as each node must be checked one by one. Meanwhile, in an array, searching for an element in an unsorted array also takes linear time (O(n)), as each element must be checked one by one.
In a linked list, cache performance is poor because the nodes are scattered across memory, which reduces cache locality. In contrast, in an array, cache performance is better because elements are stored contiguously in memory, improving cache efficiency.
Use a linked list when frequent insertions and deletions are required, especially in situations where the data size is unknown or changes dynamically. In contrast, arrays are best when fast, direct access to elements is needed (e.g., indexing) and when the data size is fixed or known in advance.
In a linked list, searching for an element in a sorted list still takes linear time (O(n)), as linked lists cannot perform binary search. Meanwhile, in an array, searching for an element in a sorted array can be done using binary search, which takes logarithmic time (O(log n)).
In a linked list, the implementation is more complex because it requires managing pointers and dynamic memory allocation for each node. On the other hand, in an array, implementation is simpler because there is no need to manage pointers or dynamic memory.

Conclusion

Both linked lists and arrays are essential data structures, each with distinct advantages. Linked lists excel in dynamic memory allocation and frequent insertions/deletions, while arrays offer fast access and simplicity. Choosing between them depends on the specific needs of your application, such as memory flexibility or quick access.

FAQS

What is the main difference between a linked list and an array?

The main difference is that arrays store elements in contiguous memory, allowing fast access, while linked lists store elements non-contiguously with pointers, requiring traversal for access.

How are elements accessed differently in an array and a linked list?

In an array, elements are accessed directly using indices (O(1) time), while in a linked list, access requires traversal (O(n) time).

What is the difference between ArrayList and a linked list?

ArrayLists offer dynamic resizing and index-based access like arrays but are slower for insertions and deletions, while linked lists excel in insertion/deletion efficiency.

What are the advantages of a linked list over an array?

Linked lists allow for dynamic resizing, efficient insertions and deletions, and memory-efficient handling of data that changes frequently, which makes them preferable in some linked list vs array comparisons.

Why use an array instead of a linked list?

Arrays are ideal when fast, direct access to elements (O(1)) is needed, and the number of elements is fixed or known ahead of time, which makes them a strong choice in linked list vs array situations.

How does memory allocation differ between a linked list and an array?

Linked lists use non-contiguous memory with separate nodes connected by pointers, while arrays allocate contiguous memory for all elements.

Can you change the size of an array dynamically?

No, arrays have a fixed size. To change the size, you must create a new array and copy the existing elements.

Why is accessing elements faster in an array compared to a linked list?

Arrays allow direct access via indices, whereas linked lists require traversal through each node, making access slower.

What happens when you delete or insert elements in the middle of an array?

Insertions and deletions in the middle of an array require shifting elements, which results in a time complexity of O(n).

How does the cache performance of a linked list compare to an array?

Arrays have better cache performance due to contiguous memory allocation, while linked lists suffer from poor cache locality because nodes are scattered in memory.

What is the complexity of insertion and deletion in linked lists compared to arrays?

In a linked list, insertion and deletion can be done in constant time (O(1)) at the beginning or middle, while arrays require shifting elements (O(n)).