Linked List Operations: Traverse, Insert and Delete (2024)

There are various linked list operations that allow us to perform different actions on linked lists. For example, the insertion operation adds a new element to the linked list.

Here's a list of basic linked list operations that we will cover in this article.

Traversal - access each element of the linked list
Insertion - adds a new element to the linked list
Deletion - removes the existing elements
Search - find a node in the linked list
Sort - sort the nodes of the linked list

Before you learn about linked list operations in detail, make sure to know about Linked List first.

Things to Remember about Linked List

head points to the first node of the linked list
next pointer of the last node is NULL, so if the next current node is NULL, we have reached the end of the linked list.

In all of the examples, we will assume that the linked list has three nodes 1 --->2 --->3 with node structure as below:

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

Traverse a Linked List

Displaying the contents of a linked list is very simple. We keep moving the temp node to the next one and display its contents.

When temp is NULL, we know that we have reached the end of the linked list so we get out of the while loop.

struct node *temp = head;printf("\n\nList elements are - \n");while(temp != NULL) { printf("%d --->",temp->data); temp = temp->next;}

The output of this program will be:

Insert Elements to a Linked List

You can add elements to either the beginning, middle or end of the linked list.

1. Insert at the beginning

Allocate memory for new node
Store data
Change next of new node to point to head
Change head to point to recently created node

struct node *newNode;newNode = malloc(sizeof(struct node));newNode->data = 4;newNode->next = head;head = newNode;

2. Insert at the End

Allocate memory for new node
Store data
Traverse to last node
Change next of last node to recently created node

struct node *newNode;newNode = malloc(sizeof(struct node));newNode->data = 4;newNode->next = NULL;struct node *temp = head;while(temp->next != NULL){ temp = temp->next;}temp->next = newNode;

3. Insert at the Middle

Allocate memory and store data for new node
Traverse to node just before the required position of new node
Change next pointers to include new node in between

struct node *newNode;newNode = malloc(sizeof(struct node));newNode->data = 4;struct node *temp = head;for(int i=2; i < position; i++) { if(temp->next != NULL) { temp = temp->next; }}newNode->next = temp->next;temp->next = newNode;

Delete from a Linked List

You can delete either from the beginning, end or from a particular position.

1. Delete from beginning

Point head to the second node

head = head->next;

2. Delete from end

Traverse to second last element
Change its next pointer to null

struct node* temp = head;while(temp->next->next!=NULL){ temp = temp->next;}temp->next = NULL;

3. Delete from middle

Traverse to element before the element to be deleted
Change next pointers to exclude the node from the chain

for(int i=2; i< position; i++) { if(temp->next!=NULL) { temp = temp->next; }}temp->next = temp->next->next;

Search an Element on a Linked List

You can search an element on a linked list using a loop using the following steps. We are finding item on a linked list.

Make head as the current node.
Run a loop until the current node is NULL because the last element points to NULL.
In each iteration, check if the key of the node is equal to item. If it the key matches the item, return true otherwise return false.

// Search a nodebool searchNode(struct Node** head_ref, int key) { struct Node* current = *head_ref; while (current != NULL) { if (current->data == key) return true; current = current->next; } return false;}

Sort Elements of a Linked List

We will use a simple sorting algorithm, Bubble Sort, to sort the elements of a linked list in ascending order below.

Make the head as the current node and create another node index for later use.
If head is null, return.
Else, run a loop till the last node (i.e. NULL).
In each iteration, follow the following step 5-6.
Store the next node of current in index.
Check if the data of the current node is greater than the next node. If it is greater, swap current and index.

Check the article on bubble sort for better understanding of its working.

// Sort the linked listvoid sortLinkedList(struct Node** head_ref) { struct Node *current = *head_ref, *index = NULL; int temp; if (head_ref == NULL) { return; } else { while (current != NULL) { // index points to the node next to current index = current->next; while (index != NULL) { if (current->data > index->data) { temp = current->data; current->data = index->data; index->data = temp; } index = index->next; } current = current->next; } }}

LinkedList Operations in Python, Java, C, and C++

Python

Java

C++

# Linked list operations in Python# Create a nodeclass Node: def __init__(self, data): self.data = data self.next = Noneclass LinkedList: def __init__(self): self.head = None # Insert at the beginning def insertAtBeginning(self, new_data): new_node = Node(new_data) new_node.next = self.head self.head = new_node # Insert after a node def insertAfter(self, prev_node, new_data): if prev_node is None: print("The given previous node must inLinkedList.") return new_node = Node(new_data) new_node.next = prev_node.next prev_node.next = new_node # Insert at the end def insertAtEnd(self, new_data): new_node = Node(new_data) if self.head is None: self.head = new_node return last = self.head while (last.next): last = last.next last.next = new_node # Deleting a node def deleteNode(self, position): if self.head is None: return temp = self.head if position == 0: self.head = temp.next temp = None return # Find the key to be deleted for i in range(position - 1): temp = temp.next if temp is None: break # If the key is not present if temp is None: return if temp.next is None: return next = temp.next.next temp.next = None temp.next = next # Search an element def search(self, key): current = self.head while current is not None: if current.data == key: return True current = current.next return False # Sort the linked list def sortLinkedList(self, head): current = head index = Node(None) if head is None: return else: while current is not None: # index points to the node next to current index = current.next while index is not None: if current.data > index.data: current.data, index.data = index.data, current.data index = index.next current = current.next # Print the linked list def printList(self): temp = self.head while (temp): print(str(temp.data) + " ", end="") temp = temp.nextif __name__ == '__main__': llist = LinkedList() llist.insertAtEnd(1) llist.insertAtBeginning(2) llist.insertAtBeginning(3) llist.insertAtEnd(4) llist.insertAfter(llist.head.next, 5) print('linked list:') llist.printList() print("\nAfter deleting an element:") llist.deleteNode(3) llist.printList() print() item_to_find = 3 if llist.search(item_to_find): print(str(item_to_find) + " is found") else: print(str(item_to_find) + " is not found") llist.sortLinkedList(llist.head) print("Sorted List: ") llist.printList()

// Linked list operations in Javaclass LinkedList { Node head; // Create a node class Node { int data; Node next; Node(int d) { data = d; next = null; } } // Insert at the beginning public void insertAtBeginning(int new_data) { // insert the data Node new_node = new Node(new_data); new_node.next = head; head = new_node; } // Insert after a node public void insertAfter(Node prev_node, int new_data) { if (prev_node == null) { System.out.println("The given previous node cannot be null"); return; } Node new_node = new Node(new_data); new_node.next = prev_node.next; prev_node.next = new_node; } // Insert at the end public void insertAtEnd(int new_data) { Node new_node = new Node(new_data); if (head == null) { head = new Node(new_data); return; } new_node.next = null; Node last = head; while (last.next != null) last = last.next; last.next = new_node; return; } // Delete a node void deleteNode(int position) { if (head == null) return; Node temp = head; if (position == 0) { head = temp.next; return; } // Find the key to be deleted for (int i = 0; temp != null && i < position - 1; i++) temp = temp.next; // If the key is not present if (temp == null || temp.next == null) return; // Remove the node Node next = temp.next.next; temp.next = next; } // Search a node boolean search(Node head, int key) { Node current = head; while (current != null) { if (current.data == key) return true; current = current.next; } return false; } // Sort the linked list void sortLinkedList(Node head) { Node current = head; Node index = null; int temp; if (head == null) { return; } else { while (current != null) { // index points to the node next to current index = current.next; while (index != null) { if (current.data > index.data) { temp = current.data; current.data = index.data; index.data = temp; } index = index.next; } current = current.next; } } } // Print the linked list public void printList() { Node tnode = head; while (tnode != null) { System.out.print(tnode.data + " "); tnode = tnode.next; } } public static void main(String[] args) { LinkedList llist = new LinkedList(); llist.insertAtEnd(1); llist.insertAtBeginning(2); llist.insertAtBeginning(3); llist.insertAtEnd(4); llist.insertAfter(llist.head.next, 5); System.out.println("Linked list: "); llist.printList(); System.out.println("\nAfter deleting an element: "); llist.deleteNode(3); llist.printList(); System.out.println(); int item_to_find = 3; if (llist.search(llist.head, item_to_find)) System.out.println(item_to_find + " is found"); else System.out.println(item_to_find + " is not found"); llist.sortLinkedList(llist.head); System.out.println("\nSorted List: "); llist.printList(); }}

// Linked list operations in C#include <stdio.h>#include <stdlib.h>// Create a nodestruct Node { int data; struct Node* next;};// Insert at the beginningvoid insertAtBeginning(struct Node** head_ref, int new_data) { // Allocate memory to a node struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); // insert the data new_node->data = new_data; new_node->next = (*head_ref); // Move head to new node (*head_ref) = new_node;}// Insert a node after a nodevoid insertAfter(struct Node* prev_node, int new_data) { if (prev_node == NULL) { printf("the given previous node cannot be NULL"); return; } struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); new_node->data = new_data; new_node->next = prev_node->next; prev_node->next = new_node;}// Insert the the endvoid insertAtEnd(struct Node** head_ref, int new_data) { struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); struct Node* last = *head_ref; /* used in step 5*/ new_node->data = new_data; new_node->next = NULL; if (*head_ref == NULL) { *head_ref = new_node; return; } while (last->next != NULL) last = last->next; last->next = new_node; return;}// Delete a nodevoid deleteNode(struct Node** head_ref, int key) { struct Node *temp = *head_ref, *prev; if (temp != NULL && temp->data == key) { *head_ref = temp->next; free(temp); return; } // Find the key to be deleted while (temp != NULL && temp->data != key) { prev = temp; temp = temp->next; } // If the key is not present if (temp == NULL) return; // Remove the node prev->next = temp->next; free(temp);}// Search a nodeint searchNode(struct Node** head_ref, int key) { struct Node* current = *head_ref; while (current != NULL) { if (current->data == key) return 1; current = current->next; } return 0;}// Sort the linked listvoid sortLinkedList(struct Node** head_ref) { struct Node *current = *head_ref, *index = NULL; int temp; if (head_ref == NULL) { return; } else { while (current != NULL) { // index points to the node next to current index = current->next; while (index != NULL) { if (current->data > index->data) { temp = current->data; current->data = index->data; index->data = temp; } index = index->next; } current = current->next; } }}// Print the linked listvoid printList(struct Node* node) { while (node != NULL) { printf(" %d ", node->data); node = node->next; }}// Driver programint main() { struct Node* head = NULL; insertAtEnd(&head, 1); insertAtBeginning(&head, 2); insertAtBeginning(&head, 3); insertAtEnd(&head, 4); insertAfter(head->next, 5); printf("Linked list: "); printList(head); printf("\nAfter deleting an element: "); deleteNode(&head, 3); printList(head); int item_to_find = 3; if (searchNode(&head, item_to_find)) { printf("\n%d is found", item_to_find); } else { printf("\n%d is not found", item_to_find); } sortLinkedList(&head); printf("\nSorted List: "); printList(head);}

// Linked list operations in C++#include <stdlib.h>#include <iostream>using namespace std;// Create a nodestruct Node { int data; struct Node* next;};void insertAtBeginning(struct Node** head_ref, int new_data) { // Allocate memory to a node struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); // insert the data new_node->data = new_data; new_node->next = (*head_ref); // Move head to new node (*head_ref) = new_node;}// Insert a node after a nodevoid insertAfter(struct Node* prev_node, int new_data) { if (prev_node == NULL) { cout << "the given previous node cannot be NULL"; return; } struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); new_node->data = new_data; new_node->next = prev_node->next; prev_node->next = new_node;}// Insert at the endvoid insertAtEnd(struct Node** head_ref, int new_data) { struct Node* new_node = (struct Node*)malloc(sizeof(struct Node)); struct Node* last = *head_ref; /* used in step 5*/ new_node->data = new_data; new_node->next = NULL; if (*head_ref == NULL) { *head_ref = new_node; return; } while (last->next != NULL) last = last->next; last->next = new_node; return;}// Delete a nodevoid deleteNode(struct Node** head_ref, int key) { struct Node *temp = *head_ref, *prev; if (temp != NULL && temp->data == key) { *head_ref = temp->next; free(temp); return; } // Find the key to be deleted while (temp != NULL && temp->data != key) { prev = temp; temp = temp->next; } // If the key is not present if (temp == NULL) return; // Remove the node prev->next = temp->next; free(temp);}// Search a nodebool searchNode(struct Node** head_ref, int key) { struct Node* current = *head_ref; while (current != NULL) { if (current->data == key) return true; current = current->next; } return false;}// Sort the linked listvoid sortLinkedList(struct Node** head_ref) { struct Node *current = *head_ref, *index = NULL; int temp; if (head_ref == NULL) { return; } else { while (current != NULL) { // index points to the node next to current index = current->next; while (index != NULL) { if (current->data > index->data) { temp = current->data; current->data = index->data; index->data = temp; } index = index->next; } current = current->next; } }}// Print the linked listvoid printList(struct Node* node) { while (node != NULL) { cout << node->data << " "; node = node->next; }}// Driver programint main() { struct Node* head = NULL; insertAtEnd(&head, 1); insertAtBeginning(&head, 2); insertAtBeginning(&head, 3); insertAtEnd(&head, 4); insertAfter(head->next, 5); cout << "Linked list: "; printList(head); cout << "\nAfter deleting an element: "; deleteNode(&head, 3); printList(head); int item_to_find = 3; if (searchNode(&head, item_to_find)) { cout << endl << item_to_find << " is found"; } else { cout << endl << item_to_find << " is not found"; } sortLinkedList(&head); cout << "\nSorted List: "; printList(head);}