How To Create Linked List In Data Structure C++

Linked list Data Structure

In this tutorial, you will learn about linked list data structure and it's implementation in Python, Java, C, and C++.

A linked list is a linear data structure that includes a series of connected nodes. Here, each node stores the data and the address of the next node. For example,

You have to start somewhere, so we give the address of the first node a special name called HEAD. Also, the last node in the linked list can be identified because its next portion points to NULL.

Linked lists can be of multiple types: singly, doubly, and circular linked list. In this article, we will focus on the singly linked list. To learn about other types, visit Types of Linked List.

Note: You might have played the game Treasure Hunt, where each clue includes the information about the next clue. That is how the linked list operates.

Representation of Linked List

Let's see how each node of the linked list is represented. Each node consists:

A data item
An address of another node

We wrap both the data item and the next node reference in a struct as:

            struct node {   int data;   struct node *next; };

Understanding the structure of a linked list node is the key to having a grasp on it.

Each struct node has a data item and a pointer to another struct node. Let us create a simple Linked List with three items to understand how this works.

            /* Initialize nodes */ struct node *head; struct node *one = NULL; struct node *two = NULL; struct node *three = NULL;  /* Allocate memory */ one = malloc(sizeof(struct node)); two = malloc(sizeof(struct node)); three = malloc(sizeof(struct node));  /* Assign data values */ one->data = 1; two->data = 2; three->data=3;  /* Connect nodes */ one->next = two; two->next = three; three->next = NULL;  /* Save address of first node in head */ head = one;

If you didn't understand any of the lines above, all you need is a refresher on pointers and structs.

In just a few steps, we have created a simple linked list with three nodes.

representing linked list by connecting each node with next node using address of next node — Linked list Representation

The power of a linked list comes from the ability to break the chain and rejoin it. E.g. if you wanted to put an element 4 between 1 and 2, the steps would be:

Create a new struct node and allocate memory to it.
Add its data value as 4
Point its next pointer to the struct node containing 2 as the data value
Change the next pointer of "1" to the node we just created.

Doing something similar in an array would have required shifting the positions of all the subsequent elements.

In python and Java, the linked list can be implemented using classes as shown in the codes below.

Linked List Utility

Lists are one of the most popular and efficient data structures, with implementation in every programming language like C, C++, Python, Java, and C#.

Apart from that, linked lists are a great way to learn how pointers work. By practicing how to manipulate linked lists, you can prepare yourself to learn more advanced data structures like graphs and trees.

Linked List Implementations in Python, Java, C, and C++ Examples

                # Linked list implementation in Python   class Node:     # Creating a node     def __init__(self, item):         self.item = item         self.next = None   class LinkedList:      def __init__(self):         self.head = None   if __name__ == '__main__':      linked_list = LinkedList()      # Assign item values     linked_list.head = Node(1)     second = Node(2)     third = Node(3)      # Connect nodes     linked_list.head.next = second     second.next = third      # Print the linked list item     while linked_list.head != None:         print(linked_list.head.item, end=" ")         linked_list.head = linked_list.head.next

                // Linked list implementation in Java  class LinkedList {   // Creating a node   Node head;    static class Node {     int value;     Node next;      Node(int d) {       value = d;       next = null;     }   }    public static void main(String[] args) {     LinkedList linkedList = new LinkedList();      // Assign value values     linkedList.head = new Node(1);     Node second = new Node(2);     Node third = new Node(3);      // Connect nodess     linkedList.head.next = second;     second.next = third;      // printing node-value     while (linkedList.head != null) {       System.out.print(linkedList.head.value + " ");       linkedList.head = linkedList.head.next;     }   } }

                // Linked list implementation in C  #include <stdio.h> #include <stdlib.h>  // Creating a node struct node {   int value;   struct node *next; };  // print the linked list value void printLinkedlist(struct node *p) {   while (p != NULL) {     printf("%d ", p->value);     p = p->next;   } }  int main() {   // Initialize nodes   struct node *head;   struct node *one = NULL;   struct node *two = NULL;   struct node *three = NULL;    // Allocate memory   one = malloc(sizeof(struct node));   two = malloc(sizeof(struct node));   three = malloc(sizeof(struct node));    // Assign value values   one->value = 1;   two->value = 2;   three->value = 3;    // Connect nodes   one->next = two;   two->next = three;   three->next = NULL;    // printing node-value   head = one;   printLinkedlist(head); }

                // Linked list implementation in C++  #include <bits/stdc++.h> #include <iostream> using namespace std;  // Creating a node class Node {    public:   int value;   Node* next; };  int main() {   Node* head;   Node* one = NULL;   Node* two = NULL;   Node* three = NULL;    // allocate 3 nodes in the heap   one = new Node();   two = new Node();   three = new Node();    // Assign value values   one->value = 1;   two->value = 2;   three->value = 3;    // Connect nodes   one->next = two;   two->next = three;   three->next = NULL;    // print the linked list value   head = one;   while (head != NULL) {     cout << head->value;     head = head->next;   } }

Linked List Complexity

Time Complexity

	Worst case	Average Case
Search	O(n)	O(n)
Insert	O(1)	O(1)
Deletion	O(1)	O(1)

Space Complexity: O(n)

Linked List Applications

Dynamic memory allocation
Implemented in stack and queue
In undo functionality of softwares
Hash tables, Graphs

1. Tutorials

Linked List Operations (Traverse, Insert, Delete)
Types of Linked List
Java LinkedList

2. Examples

Get the middle element of Linked List in a single iteration
Convert the Linked List into an Array and vice versa
Detect loop in a Linked List