Data Structures

Data Structure

A data structure is a storage used to store and organize data. It is a way of arranging data on a computer so that it can be accessed and updated efficiently. A data structure is not only used for organizing the data. It is also used for processing, retrieving, and storing data. There are different basic and advanced types of data structures that are used in almost every program or software system that has been developed.

Linked List

A linked list is a linear data structure (like arrays) where each element is a separate object. A linked list is made up of two items that are data and a reference to the next node. A reference to the next node is given with the help of pointers and data is the value of a node. Each node contains data and links to the other nodes. It is an ordered collection of data elements called a node and the linear order is maintained by pointers. It has an upper hand over the array as the number of nodes i.e. the size of the linked list is not fixed and can grow and shrink as and when required, unlike arrays.

Circular Linked List

Circular linked list is a linked list where all nodes are connected to form a circle. There is no NULL at the end. A circular linked list can be a singly circular linked list or a doubly circular linked list. The advantage of this data structure is that any node can be made as starting node. This is useful in the implementation of the circular queues in the linked list. Eg. 1->2->3->1 [The next pointer of the last node is pointing to the first]

Linear data structure

Data structure in which data elements are arranged sequentially or linearly, where each element is attached to its previous and next adjacent elements, is called a linear data structure. Examples of linear data structures are array, stack, queue, linked list, etc.

Non-linear data structure

Data structures where data elements are not placed sequentially or linearly are called non-linear data structures. In a non-linear data structure, we can't traverse all the elements in a single run only. Examples of non-linear data structures are trees and graphs.

Dynamic data structure

In dynamic data structure, the size is not fixed. It can be randomly updated during the runtime which may be considered efficient concerning the memory (space) complexity of the code. Examples of this data structure are queue, stack, etc.

Doubly Linked List

In this type of Linked list, there are two references associated with each node, One of the reference points to the next node and one to the previous node. The advantage of this data structure is that we can traverse in both directions and for deletion, we don't need to have explicit access to the previous node. Eg. NULL<-1<->2<->3->NULL

Singly Linked List

In this type of linked list, every node stores address or reference of the next node in the list and the last node has the next address or reference as NULL. For example 1->2->3->4->NULL

Array

Let size of array be n. Accessing Time: O(1) [This is possible because elements are stored at contiguous locations] Search Time: O(n) for Sequential Search: O(log n) for Binary Search [If Array is sorted] Insertion Time: O(n) [The worst case occurs when insertion happens at the Beginning of an array and requires shifting all of the elements] Deletion Time: O(n) [The worst case occurs when deletion happens at the Beginning of an array and requires shifting all of the elements]

Types of Linked List

Singly Linked List Doubly Linked List Circular Linked List Circular Doubly Linked List

Static data structure

Static data structure has a fixed memory size. It is easier to access the elements in a static data structure. An example of this data structure is an array.

Circular Doubly Linked List

The circular doubly linked list is a combination of the doubly linked list and the circular linked list. It means that this linked list is bidirectional and contains two pointers and the last pointer points to the first pointer. Accessing time of an element : O(n) Search time of an element : O(n) Insertion of an Element : O(1) [If we are at the position where we have to insert an element] Deletion of an Element : O(1) [If we know address of node previous to the node to be deleted]