Difference Between Array And Linked List Data Structures

Array and Linked Lists are types of data structures. A data structure is a method for organizing a set of data. The structure is defined by how the data is stored and how operations, such as data access, insertion and deletion are performed on the stored data. Data structures are essential tools for programmers, as each structure has a set of benefits that make it useful for solving certain types of problem.

What Is Array Data Structure?

An Array data structure or simply Array, is a data structure consisting of a collection of elements (values or variables), each identified by at least one array index or key. An Array is stored such that the position of each element can be computed from its index tuple by a mathematical formula.

Arrays are useful mostly because the element indices can be computed at run time. Among other things, this feature allows a single iterative statement to process arbitrary many elements of an array. In this regard, the elements of an array data structure are required to have the same size and should use the same data representation. The set of valid index tuples and the addresses of the elements are usually, but not always, fixed while the array is in use.

Types Of Array

Single/One Dimensional (1-D) arrays or Linear arrays. In these arrays, each element is represented by a single subscript.
Two dimensional (2-D) arrays or Matrix arrays. In these arrays, each element is represented by a single subscript.
Three Dimension Arrays. In these arrays, each element is represented by three subscripts.

What You Need To Know Array Data Structure

An array is the data structure that contains a collection of similar type data elements.
Memory is allocated as soon as the array is declared, at compile time. This is referred to as static memory allocation.
Array can be single dimensional, two dimensional or three dimensional.
The size of array must be specified at time of array declaration/initialization.
Memory requirement is limited due to actual data being stored within index in the Array.
Insertion and deletion operations take some time since the memory locations are consecutive and fixed.
In array, each element is independent, no connection with previous element or with its location.
In array, elements are stored in consecutive memory locations, so while inserting elements; we have to create space for insertion.
Array supports Random Access, which means, elements can be accessed directly using their index, like arr [0] for 1^st element, arr [4] for 5^th element etc. Hence, accessing elements in an array is fast with a constant time complexity of 0(1).
Array gets memory allocated in stack section.
Memory utilization is inefficient in the array.
Binary and linear search are employed in array.

What Is Linked List Data Structure?

A linked list is a linear data structure where each element is a separate object. Linked list elements are not stored at contagious location; the elements are linked using pointers. Each node of a list is made up of two items- the data and a reference to the next node. The last node has a reference to null.

Linked Lists are among the simplest and most common data structures. They can be used to implement several other common abstract data types, including lists, stacks, queues, associative arrays and S-expressions, though these data structures can be implemented directly without using a linked list as the basis.

Types of Linked List

Simple Linked List-item navigation is forward only.
Doubly Linked List-Items can be navigated forward and backward.
Circular Linked List-Last item contains link of the first element as next and the first element has a link to the last element as previous.

Applications Of Linked List

Linked lists can be used to implement Hash Tables-Each Bucket of the hash table can be a linked list (Open Chain Hashing).
Linked Lists can be used to implement Graphs.
Linked list can be used to implement Stacks, Queues, and Trees.

What You Need To Know About Linked List Data Structure

The linked list is considered as non-primitive data structure contains a collection of unordered Linked elements referred to as nodes.
Memory is allocated at runtime as and when a new node is added. It’s also known as Dynamic Memory Allocation.
Linked List can be linear (Singly), Doubly or Circular linked list.
Size of a Linked List is variable. It grows at runtime, as more nodes are added to it.
Memory requirement needs in Linked List are more due to storage of additional next and previous referencing elements.
Insertion and deletion operations are fast and easy in a Linked List because only value of pointer is needed to change. In case of linked list, a new element is stored at the first free and available memory location, with only a single overhead step of storing the address of memory location in previous node of linked list.
In Linked List, locations or address of elements is stored in the link part of previous element/node or elements point to the next, previous or maybe both nodes.
In linked list, elements can be stored at any available place as address of node is stored in previous node of the linked list, hence forming a link between the two nodes/elements.
Linked list supports Sequential Access, which means to access any element/node in a linked list; we have to sequentially traverse the complete linked list, up to that element. To access n^th element of a linked list, time complexity is 0 (n).
Linked list gets memory allocated in heap section.
In addition memory utilization is efficient in the linked list.
Only linear search is used in linked list data structure.

Also Read: Difference Between Array And Pointer

Difference Between Array And Linked List In Tabular Form

BASIS OF COMPARISON	ARRAY	LINKED LIST
Description	An array is the data structure that contains a collection of similar type data elements.	The linked list is considered as non-primitive data structure contains a collection of unordered Linked elements referred to as nodes.
Memory Allocation	Memory is allocated as soon as the array is declared, at compile time. This is referred to as static memory allocation.	Memory is allocated at runtime as and when a new node is added. It’s also known as Dynamic Memory Allocation.
Types	Array can be single dimensional, two dimensional or three dimensional.	Linked List can be linear (Singly), Doubly or Circular linked list.
Size	The size of array must be specified at time of array declaration/initialization.	Size of a Linked List is variable. It grows at runtime, as more nodes are added to it.
Memory Requirement	Memory requirement is limited due to actual data being stored within index in the Array.	Memory requirement needs in Linked List are more due to storage of additional next and previous referencing elements.
Insertion And Deletion Operations	Insertion and deletion operations take some time since the memory locations are consecutive and fixed.	Insertion and deletion operations are fast and easy in a Linked List because only value of pointer is needed to change.
Storage Of Elements	In array, elements are stored in consecutive memory locations, so while inserting elements; we have to create space for insertion.	In linked list, elements can be stored at any available place as address of node is stored in previous node of the linked list, hence forming a link between the two nodes/elements.
Type Of Access Supported	Array supports Random Access, which means, elements can be accessed directly using their index, like arr [0] for 1^st element, arr [4] for 5^th element etc. Hence, accessing elements in an array is fast with a constant time complexity of 0(1).	Linked list supports Sequential Access, which means to access any element/node in a linked list; we have to sequentially traverse the complete linked list, up to that element. To access n^th element of a linked list, time complexity is 0 (n).
Memory Allocation Section	Array gets memory allocated in stack section.	Linked list gets memory allocated in heap section.
Memory Utilization	Memory utilization is inefficient in the array.	In addition memory utilization is efficient in the linked list.
Type Of Search	Binary and linear search are employed in array.	Only linear search is used in linked list data structure.

Also Read: Difference Between Stack And Heap In C

Advantages of Linked List

Suitable for any type of insertion.
Data structures like Stacks, Queues and trees can easily be implemented using linked list.
Objects can be traversed using for loop, iterator, listIterator, descendingIterator.
Can use dispersed vacant memory location.
Internally follows doubly linked list data structure.
Size of linked lists is not fixed; they can expand and shrink during run time.
Memory allocation is done during run-time (no need to allocate any fixed memory).
Insertion and deletion operations are fast and easier in linked lists.
Memory allocation is allocated at Run-time.
Linked list can hold more than one value at a time.

Disadvantages Of Linked List

The nodes in the linked list can be added and deleted from the list.
It is a complex process in modifying the node in a linked list.
Pointers take extra memory in linked list data structure.
Random access is not allowed.
Insertion, deletion operations are costlier in linked list.
Traversing from reverse is not possible in singly linked lists.

Advantages Of Array

Arrays are linear data structures.
Array has homogenous values.
Array elements can be modified easily by identifying the index value.
Array elements cannot be added, deleted once it is declared.
Arrays have better cache locality that can make a pretty big difference in performance.
Array can hold only one value at a time.
Array can be used to implement other data structures like linked lists, stacks, queues, trees, graphs etc.

Disadvantages Of Array

In array, there is ineffective memory utilization.
The elements of array are stored in consecutive memory locations. So insertions and deletions are very difficult and time consuming.
Since array is of fixed size, if we allocate more memory than requirement, then the memory space will be wasted. And if we allocate less memory than requirement, then it will create problem.