Deletion in Singly Linked List in C++

What is deletion in singly linked list in C++?

Deletion in singly linked in C++ can be simplified as deleting a node from an already constructed linked list. We can perform three different types of deletion operations on a singly linked-

  • Deleting the beginning
  • Deletion from a specific position
  • Deletion from end
delete

Types of deletion in singly linked list

There can be two different approaches for deletion –

We will look at both of them in this page and understand how to code them.

Deletion in a Singly Linked List for a Value

Let’s have a look at the program

This method uses non-member function and explicit passing of head in the functions
Run
#include<iostream>
using namespace std;

class Node
{
    public:
    int data;
    Node *next;
};

void insert(Node** head, int data){

    Node* new_node = new Node();

    new_node->data = data;
    new_node->next = *head;
    *head = new_node;
}
void deleteNode(Node** head, int delVal)
{
    Node* temp = *head;
    Node* previous;
    
    if(temp == NULL){
        cout << "Can't delete Linked List empty" << endl; 
        return; 
    } 

    // Case when there is only 1 node in the list 
    if(temp->next==NULL)
    {
        *head = NULL;
        free(temp);
        cout << "Deleted: " << delVal << endl; 
        return; 
    } // if the head node itself needs to be deleted 
    if(temp->data==delVal)
    {
        *head = temp->next; //changing head to next in the list
        cout << "Deleted: " << temp->data << endl; 
        free(temp); 
        return; 
    } 

    // traverse until we find the value to be deleted or LL ends 
    while (temp != NULL && temp->data != delVal) 
    { 
        // store previous link node as we need to change its next val
        previous = temp; 
        temp = temp->next; 
    }

    // if value is not present then
    // temp will have traversed to last node NULL
    if(temp==NULL)
    {
        cout << "Value not found" << endl; 
        return; 
    } 

    // for node to be deleted : temp lets call it nth node 
    // assign (n-1)th node's next to (n+1)th node 
    previous->next = temp->next;
    free(temp);
    cout << "Deleted: " << delVal << endl;
}
void display(Node* node){
    
    cout << "\nLinked List : " ;
    
    //as linked list will end when Node is Null
    while(node!=NULL){
        cout << node->data << " "; 
        node = node->next;
    }
    cout << endl;
}

int main(){

    Node* head = NULL;

    insert(&head, 1);
    insert(&head, 2);
    insert(&head, 3);
    insert(&head, 4);
    insert(&head, 5);
    insert(&head, 6);

    display(head);
    
    deleteNode(&head, 4);
    display(head);

    deleteNode(&head, 10);
    deleteNode(&head, 1);
    deleteNode(&head, 5);
    deleteNode(&head, 6);
    display(head);
    
    return 0;  
}

Output

Linked List : 6 5 4 3 2 1 
Deleted: 4

Linked List : 6 5 3 2 1 
Value not found
Deleted: 1
Deleted: 5
Deleted: 6

Linked List : 3 2
This method uses member function head need not be passed as its member variable of class
Run
#include<iostream>
using namespace std;

class Node
{
    public:
    int data;
    Node *next;
};

class LinkedList
{
    private:
        Node* head;
    public:
        LinkedList() { // constructor
        head = NULL;
    }
        void insert(int data);
        void display();
        void deleteNode(int data);
};

void LinkedList::insert(int data){

    Node* new_node = new Node();
    
    new_node->data = data;
    new_node->next = head;
    head = new_node;
}
void LinkedList::deleteNode(int delVal)
{
    Node* temp = head;
    Node* previous;
    
    if(temp == NULL){
        cout << "Can't delete Linked List empty" << endl; 
        return; 
    } 

    // Case when there is only 1 node in the list 
    if(temp->next==NULL)
    {
        head = NULL;
        free(temp);
        cout << "Deleted: " << delVal << endl; 
        return; 
    } 

    // if the head node itself needs to be deleted 
    if(temp->data==delVal)
    {
        head = temp->next; //changing head to next in the list
        cout << "Deleted: " << temp->data << endl; 
        free(temp); 
        return; 
    } 

    // traverse until we find the value to be deleted or LL ends 
    while (temp != NULL && temp->data != delVal) 
    { 
        // store previous link node as we need to change its next val
        previous = temp; 
        temp = temp->next; 
    }

    // if value is not present then
    // temp will have traversed to last node NULL
    if(temp==NULL)
    {
        cout << "Value not found" << endl; 
        return; 
    } 

    // for node to be deleted : temp lets call it nth node 
    // assign (n-1)th node's next to (n+1)th node 
    previous->next = temp->next;
    free(temp);
    cout << "Deleted: " << delVal << endl;
}
void LinkedList::display(){
    
    Node* node = new Node();
    node = head;
    
    cout << "\nLinked List : " ;
    
    //as linked list will end when Node is Null
    while(node!=NULL){
        cout << node->data << " "; 
        node = node->next;
    }
    cout << endl; 
} 

int main() { 
    LinkedList* list = new LinkedList(); 
    list->insert(1);
    list->insert(2);
    list->insert(3);
    list->insert(4);
    list->insert(5);
    list->insert(6);

    list->display();
    
    list->deleteNode(4);
    list->display();

    list->deleteNode(10);
    list->deleteNode(1);
    list->deleteNode(5);
    list->deleteNode(6);
    list->display();
    
    return 0;  
}

Output

Linked List : 6 5 4 3 2 1
Deleted: 4
Linked List : 6 5 3 2 1 Value not found Deleted: 1 Deleted: 5 Deleted: 6 Linked List : 3 2

Deletion in a Singly Linked List in C++ (For a Position)

Deletion can be performed at the following positions –

Below we will write a program that will handle all the above cases in a single function, however, if you wish to write individual functions for each you can check the pages hyperlinked above.

This program works with concept of non member functions and explicit passing of head.

#include<iostream>
using namespace std;

class Node
{
    public:
    int data;
    Node *next;
};

void insert(Node** head, int data){

    Node* new_node = new Node();

    new_node->data = data;
    new_node->next = *head;
    *head = new_node;
}

int calcSize(Node* node){
    int size=0;

    while(node!=NULL){
        node = node->next;
        size++;
    }
    return size;
}

void deletepos(Node** head, int pos)
{
    Node* temp = *head;
    Node* previous;

    int size = calcSize(*head);

    if(pos < 1 || pos > size){
        printf("Enter valid position\n");

        return;
    }
    
    //if the head node itself needs to be deleted
    if(pos == 1){
        //changing head to next in the list
        *head = temp->next; 
        cout << "Deleted Item: " << temp->data << endl; 
free(temp);
return;
}

//run until we find the value to be deleted in the list
while (--pos) {
// store previous link node as we need to change its next val
previous = temp;
temp = temp->next; } // (pos-1)th node's next assigned to (pos+1)nth node previous->next = temp->next; cout << "Deleted Item: " << temp->data << endl; free(temp); } void display(Node* node){ cout << "\nLinked List : " ; //as linked list will end when Node is Null while(node!=NULL){ cout << node->data << " ";
node = node->next; } cout << endl; } int main(){ Node* head = NULL; /*Need & i.e. address as we need to change head address */ insert(&head,10); insert(&head,20); insert(&head,30); insert(&head,40); insert(&head,50); insert(&head,60); /*No need for & i.e. address as we do not need to change head address */ display(head); deletepos(&head,1); display(head); deletepos(&head,3); display(head); deletepos(&head,4); display(head); deletepos(&head,-2); // not valid as pos negative deletepos(&head,10); // not valid as breaches size of Linked List return 0; }

Output

Linked List : 60 50 40 30 20 10 
Deleted Item: 60

Linked List : 50 40 30 20 10 
Deleted Item: 30

Linked List : 50 40 20 10 
Deleted Item: 10

Linked List : 50 40 20 
Enter valid position
Enter valid position

This program works with concept of member functions and we need not pass head as its member variable.

#include<iostream>
using namespace std;

class Node
{
    public:
    int data;
    Node *next;
};

class LinkedList
{
    private:
        Node* head;
    public:
        LinkedList() { // constructor
        head = NULL;
    }
        void insert(int data);
        void display();
        void deleteNode(int data);
        int calcSize();
        void deletepos(int pos);
};

void LinkedList::insert(int data){

    Node* new_node = new Node();
    
    new_node->data = data;
    new_node->next = head;
    head = new_node;
}
int LinkedList::calcSize(){
    int size=0;
    
    Node* node = head;
    
    while(node!=NULL){
        node = node->next;
        size++;
    }
    return size;
}

void LinkedList::deletepos(int pos)
{
    Node* temp = head;
    Node* previous;

    int size = calcSize();

    if(pos < 1 || pos > size){
        printf("Enter valid position\n");

        return;
    }
    
    //if the head node itself needs to be deleted
    if(pos == 1){
        //changing head to next in the list
        head = temp->next; 
        cout << "Deleted Item: " << temp->data << endl; 
free(temp);
return;
}

//run until we find the value to be deleted in the list
while (--pos) {
// store previous link node as we need to change its next val
previous = temp;
temp = temp->next; } // (pos-1)th node's next assigned to (pos+1)nth node previous->next = temp->next; cout << "Deleted Item: " << temp->data << endl; free(temp); } void LinkedList::display(){ Node* node = new Node(); node = head; cout << "\nLinked List : " ; //as linked list will end when Node is Null while(node!=NULL){ cout << node->data << " ";
node = node->next; } cout << endl;
}

int main() {
LinkedList* list = new LinkedList();
list->insert(1); list->insert(2); list->insert(3); list->insert(4); list->insert(5); list->insert(6); list->display(); list->deletepos(1); list->display(); list->deletepos(3); list->display(); list->deletepos(4); list->display(); list->deletepos(-2); // not valid as pos negative list->deletepos(10); // not valid as breaches size of Linked List return 0; }

Output

Linked List : 6 5 4 3 2 1 
Deleted Item: 6

Linked List : 5 4 3 2 1 
Deleted Item: 3

Linked List : 5 4 2 1 
Deleted Item: 1

Linked List : 5 4 2 
Enter valid position
Enter valid position
Linked List in C++ meme 2

Singly Linked List

  • Introduction to Linked List in Data Structure
    Click Here
  • Linked List in –
    C | C++ | Java
  • Singly Linked List in –
    C | C++ | Java
  • Insertion in singly Linked List –
    C | C++ | Java
  • Insertion at beginning in singly Linked List  –
    C | C++Java
  • Insertion at nth position in singly Linked List  –
    C | C++Java
  • Insertion at end in singly Linked List  –
    C | C++Java
  • Deletion in singly Linked List  –
    C | C++Java
  • Deletion from beginning in singly linked list :
    C | C++ | Java
  • Deletion from nth position in singly linked list :
    C | C++ | Java
  • Deletion from end in singly linked list :
    C | C++ | Java
  • Linked List Insertion and Deletion –
    C | C++Java
  • Reverse a linked list without changing links between nodes (Data reverse only) –
    C | C++Java
  • Reverse a linked list by changing links between nodes –
    C | C++Java
  • Print reverse of a linked list without actually reversing –
    C |C++Java
  • Print reverse of a linked list without actually reversing –
    C |C++Java
  • Insertion in the middle Singly Linked List –
    C | C++Java
  • Insertion in a Sorted Linked List –
    C | C++Java
  • Delete alternate nodes of a Linked List –
    C | C++Java
  • Find middle of the linked list –
    C | C++Java
  • Reverse a linked list in groups of given size –
    C | C++Java
  • Find kth node from end of the linked list –
    C | C++Java
  • Append the last n nodes of a linked list to the beginning of the list –
    C | C++Java
  • Check whether linked list is palindrome or not –
    C | C++Java
  • Fold a Linked List –
    C | C++Java
  • Insert at given Position –
    C | C++Java
  • Deletion at given Position –
    C | C++Java

Singly Linked List

  • Introduction to Linked List in Data Structure
  • Linked List in – C | C++ | Java
  • Singly Linked List in – C | C++ | Java
  • Insertion in singly Linked List – C | C++ | Java
    • Insertion at beginning in singly Linked List  – C | C++Java
    • Insertion at nth position in singly Linked List  – C | C++Java
    • Insertion at end in singly Linked List  – C | C++Java
  • Deletion in singly Linked List  – C | C++Java
    • Deletion from beginning in singly linked list : C | C++ | Java
    • Deletion from nth position in singly linked list : C | C++ | Java
    • Deletion from end in singly linked list : C | C++ | Java
  • Reverse a linked list without changing links between nodes (Data reverse only) – C | C++Java
  • Linked List Insertion and Deletion – C | C++Java
  • Reverse a linked list by changing links between nodes – C | C++Java
  • Linked List insertion in the middle – C | C++Java
  • Print reverse of a linked list without actually reversing – C |C++ | Java
  • Search an element in a linked list – C | C++Java
  • Insertion in a Sorted Linked List – C | C++Java
  • Delete alternate nodes of a Linked List – C | C++Java
  • Find middle of the linked list – C | C++Java
  • Reverse a linked list in groups of given size – C | C++Java
  • Find kth node from end of the linked list – C | C++Java
  • Append the last n nodes of a linked list to the beginning of the list – C | C++Java
  • Check whether linked list is palindrome or not – C | C++Java
  • Fold a Linked List – C | C++Java
  • Insert at a given position – C | C++Java
  • Delete at a given position – C | C++Java