Delete a Doubly Linked List node at a given position

Given a doubly linked list and a position n. The task is to delete the node at the given position n from the beginning.

Initial doubly linked list



Doubly Linked List after deletion of node at position n = 2

Approach: Following are the steps:

  1. Get the pointer to the node at position n by traversing the doubly linked list up to the nth node from the beginning.
  2. Delete the node using the pointer obtained in Step 1. Refer this post.

C++

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/* C++ implementation to delete a doubly Linked List node 
   at the given position */
#include <bits/stdc++.h>
  
using namespace std;
  
/* a node of the doubly linked list */
struct Node {
    int data;
    struct Node* next;
    struct Node* prev;
};
  
/* Function to delete a node in a Doubly Linked List.
   head_ref --> pointer to head node pointer.
   del  -->  pointer to node to be deleted. */
void deleteNode(struct Node** head_ref, struct Node* del)
{
    /* base case */
    if (*head_ref == NULL || del == NULL)
        return;
  
    /* If node to be deleted is head node */
    if (*head_ref == del)
        *head_ref = del->next;
  
    /* Change next only if node to be deleted is NOT 
       the last node */
    if (del->next != NULL)
        del->next->prev = del->prev;
  
    /* Change prev only if node to be deleted is NOT 
       the first node */
    if (del->prev != NULL)
        del->prev->next = del->next;
  
    /* Finally, free the memory occupied by del*/
    free(del);
}
  
/* Function to delete the node at the given position
   in the doubly linked list */
void deleteNodeAtGivenPos(struct Node** head_ref, int n)
{
    /* if list in NULL or invalid position is given */
    if (*head_ref == NULL || n <= 0)
        return;
  
    struct Node* current = *head_ref;
    int i;
  
    /* traverse up to the node at position 'n' from
       the beginning */
    for (int i = 1; current != NULL && i < n; i++)
        current = current->next;
  
    /* if 'n' is greater than the number of nodes
       in the doubly linked list */
    if (current == NULL)
        return;
  
    /* delete the node pointed to by 'current' */
    deleteNode(head_ref, current);
}
  
/* Function to insert a node at the beginning 
   of the Doubly Linked List */
void push(struct Node** head_ref, int new_data)
{
    /* allocate node */
    struct Node* new_node = 
         (struct Node*)malloc(sizeof(struct Node));
  
    /* put in the data  */
    new_node->data = new_data;
  
    /* since we are adding at the beginning,
    prev is always NULL */
    new_node->prev = NULL;
  
    /* link the old list off the new node */
    new_node->next = (*head_ref);
  
    /* change prev of head node to new node */
    if ((*head_ref) != NULL)
        (*head_ref)->prev = new_node;
  
    /* move the head to point to the new node */
    (*head_ref) = new_node;
}
  
/* Function to print nodes in a given doubly
   linked list */
void printList(struct Node* head)
{
    while (head != NULL) {
        cout << head->data << " ";
        head = head->next;
    }
}
  
/* Driver program to test above functions*/
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
  
    /* Create the doubly linked list 10<->8<->4<->2<->5 */
    push(&head, 5);
    push(&head, 2);
    push(&head, 4);
    push(&head, 8);
    push(&head, 10);
  
    cout << "Doubly linked list before deletion:n";
    printList(head);
  
    int n = 2;
  
    /* delete node at the given position 'n' */
    deleteNodeAtGivenPos(&head, n);
  
    cout << "\nDoubly linked list after deletion:n";
    printList(head);
  
    return 0;
}

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Java

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/* Java implementation to delete a doubly Linked List node 
   at the given position */
     
// A node of the doubly linked list 
class Node 
{
    int data;
    Node next, prev;
}
  
class GFG
{
    // Function to delete a node in a Doubly Linked List.
    // head_ref --> pointer to head node pointer.
    // del --> pointer to node to be deleted.
    static Node deleteNode(Node head, Node del)
    {
        // base case
        if (head == null || del == null)
            return null;
  
        // If node to be deleted is head node
        if (head == del)
            head = del.next;
  
        // Change next only if node to be 
        // deleted is NOT the last node
        if (del.next != null)
            del.next.prev = del.prev;
  
        // Change prev only if node to be 
        // deleted is NOT the first node
        if (del.prev != null)
            del.prev.next = del.next;
  
        del = null;
  
        return head;
    }
  
    // Function to delete the node at the
    // given position in the doubly linked list
    static void deleteNodeAtGivenPos(Node head, int n)
    {
        /* if list in NULL or invalid position is given */
        if (head == null || n <= 0)
            return;
  
        Node current = head;
        int i;
  
        /*
        * traverse up to the node at position 'n' from the beginning
        */
        for (i = 1; current != null && i < n; i++)
        {
            current = current.next;
        }
          
        // if 'n' is greater than the number of nodes
        // in the doubly linked list
        if (current == null)
            return;
  
        // delete the node pointed to by 'current'
        deleteNode(head, current);
    }
  
    // Function to insert a node
    // at the beginning of the Doubly Linked List
    static Node push(Node head, int new_data)
    {
        // allocate node
        Node new_node = new Node();
  
        // put in the data
        new_node.data = new_data;
  
        // since we are adding at the beginning,
        // prev is always NULL
  
        new_node.prev = null;
  
        // link the old list off the new node
        new_node.next = head;
  
        // change prev of head node to new node
        if (head != null)
            head.prev = new_node;
  
        // move the head to point to the new node
        head = new_node;
  
        return head;
    }
  
    // Function to print nodes in a
    // given doubly linked list
    static void printList(Node temp)
    {
        if (temp == null)
            System.out.print("Doubly Linked list empty");
  
        while (temp != null
        {
            System.out.print(temp.data + " ");
            temp = temp.next;
        }
        System.out.println();
    }
  
    // Driver code
    public static void main(String[] args)
    {
        // Start with the empty list
        Node head = null;
  
        // Create the doubly linked list:
        // 2<->2<->10<->8<->4<->2<->5<->2
  
        head = push(head, 2);
        head = push(head, 5);
        head = push(head, 4);
        head = push(head, 8);
        head = push(head, 10);
  
        System.out.println("Doubly linked list before deletion:");
        printList(head);
  
        int n = 2;
          
        // delete node at the given position 'n'
        deleteNodeAtGivenPos(head, n);
        System.out.println("Doubly linked list after deletion:");
        printList(head);
    }
}
  
// Thia code is contributed by Vivekkumar Singh

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C#

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/* C# implementation to delete a doubly Linked List node 
at the given position */
using System;
  
// A node of the doubly linked list 
public class Node 
    public int data; 
    public Node next, prev; 
  
class GFG 
    // Function to delete a node in a Doubly Linked List. 
    // head_ref --> pointer to head node pointer. 
    // del --> pointer to node to be deleted. 
    static Node deleteNode(Node head, Node del) 
    
        // base case 
        if (head == null || del == null
            return null
  
        // If node to be deleted is head node 
        if (head == del) 
            head = del.next; 
  
        // Change next only if node to be 
        // deleted is NOT the last node 
        if (del.next != null
            del.next.prev = del.prev; 
  
        // Change prev only if node to be 
        // deleted is NOT the first node 
        if (del.prev != null
            del.prev.next = del.next; 
  
        del = null
  
        return head; 
    
  
    // Function to delete the node at the 
    // given position in the doubly linked list 
    static void deleteNodeAtGivenPos(Node head, int n) 
    
        /* if list in NULL or invalid position is given */
        if (head == null || n <= 0) 
            return
  
        Node current = head; 
        int i; 
  
        /* 
        * traverse up to the node at position 'n' from the beginning 
        */
        for (i = 1; current != null && i < n; i++) 
        
            current = current.next; 
        
          
        // if 'n' is greater than the number of nodes 
        // in the doubly linked list 
        if (current == null
            return
  
        // delete the node pointed to by 'current' 
        deleteNode(head, current); 
    
  
    // Function to insert a node 
    // at the beginning of the Doubly Linked List 
    static Node push(Node head, int new_data) 
    
        // allocate node 
        Node new_node = new Node(); 
  
        // put in the data 
        new_node.data = new_data; 
  
        // since we are adding at the beginning, 
        // prev is always NULL 
  
        new_node.prev = null
  
        // link the old list off the new node 
        new_node.next = head; 
  
        // change prev of head node to new node 
        if (head != null
            head.prev = new_node; 
  
        // move the head to point to the new node 
        head = new_node; 
  
        return head; 
    
  
    // Function to print nodes in a 
    // given doubly linked list 
    static void printList(Node temp) 
    
        if (temp == null
            Console.Write("Doubly Linked list empty"); 
  
        while (temp != null
        
            Console.Write(temp.data + " "); 
            temp = temp.next; 
        
        Console.WriteLine(); 
    
  
    // Driver code 
    public static void Main(String []args) 
    
        // Start with the empty list 
        Node head = null
  
        // Create the doubly linked list: 
        // 2<->2<->10<->8<->4<->2<->5<->2 
  
        head = push(head, 2); 
        head = push(head, 5); 
        head = push(head, 4); 
        head = push(head, 8); 
        head = push(head, 10); 
  
        Console.WriteLine("Doubly linked list before deletion:"); 
        printList(head); 
  
        int n = 2; 
          
        // delete node at the given position 'n' 
        deleteNodeAtGivenPos(head, n); 
        Console.WriteLine("Doubly linked list after deletion:"); 
        printList(head); 
    
  
// This code is contributed by Arnab Kundu

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Output:

Doubly linked list before deletion:
10 8 4 2 5
Doubly linked list after deletion:
10 4 2 5

Time Complexity: O(n), in the worst case where n is the number of nodes in the doubly linked list.

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