Delete a Doubly Linked List node at a given position - GeeksforGeeks

26 Oct, 2021
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:
Get the pointer to the node at position n by traversing the doubly linked list up to the nth node from the beginning.Delete the node using the pointer obtained in Step 1. Refer this post.
Get the pointer to the node at position n by traversing the doubly linked list up to the nth node from the beginning.
Delete the node using the pointer obtained in Step 1. Refer this post.
C++
Java
Python
C#
Javascript
/* 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;}
/* Java implementation to delete a   doubly Linked List node   at the given position */    // A node of the doubly linked listclass Node{    int data;    Node next, prev;} class GFG{    static Node head = null;    // 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 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(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(current);    }     // Function to insert a node    // at the beginning of the Doubly Linked List    static void push(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;    }     // Function to print nodes in a    // given doubly linked list    static void printList()    {        Node temp = head;        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)    {        // Create the doubly linked list:        // 10<->8<->4<->2<->5         push(5);        push(2);        push(4);        push(8);        push(10);         System.out.println("Doubly linked "                           +"list before deletion:");        printList();         int n = 2;                 // delete node at the given position 'n'        deleteNodeAtGivenPos(n);        System.out.println("Doubly linked "                           +"list after deletion:");        printList();    }} // Thia code is contributed by Vivekkumar Singh
# Python implementation to delete# a doubly Linked List node# at the given position # A node of the doubly linked listclass Node:         # Constructor to create a new node    def __init__(self, data):        self.data = data        self.next = None        self.prev = None # Function to delete a node in a Doubly Linked List.# head_ref -. pointer to head node pointer.# del -. pointer to node to be deleted.def deleteNode(head_ref, del_):     # base case    if (head_ref == None or del_ == None):        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 != None):        del_.next.prev = del_.prev     # Change prev only if node to be deleted is NOT    # the first node    if (del_.prev != None):        del_.prev.next = del_.next             return head_ref # Function to delete the node at the given position# in the doubly linked listdef deleteNodeAtGivenPos(head_ref,n):     # if list in None or invalid position is given    if (head_ref == None or n <= 0):        return     current = head_ref    i = 1     # traverse up to the node at position 'n' from    # the beginning    while ( current != None and i < n ):        current = current.next        i = i + 1     # if 'n' is greater than the number of nodes    # in the doubly linked list    if (current == None):        return     # delete the node pointed to by 'current'    deleteNode(head_ref, current)         return head_ref # Function to insert a node at the beginning# of the Doubly Linked Listdef push(head_ref, new_data):     # allocate node    new_node = Node(0)     # put in the data    new_node.data = new_data     # since we are adding at the beginning,    #prev is always None    new_node.prev = None     # link the old list off the new node    new_node.next = (head_ref)     # change prev of head node to new node    if ((head_ref) != None):        (head_ref).prev = new_node     # move the head to point to the new node    (head_ref) = new_node         return head_ref # Function to print nodes in a given doubly# linked listdef printList(head):     while (head != None) :        print( head.data ,end= " ")        head = head.next     # Driver program to test above functions # Start with the empty listhead = None # Create the doubly linked list 10<.8<.4<.2<.5head = push(head, 5)head = push(head, 2)head = push(head, 4)head = push(head, 8)head = push(head, 10) print("Doubly linked list before deletion:")printList(head) n = 2 # delete node at the given position 'n'head = deleteNodeAtGivenPos(head, n) print("\nDoubly linked list after deletion:") printList(head) # This code is contributed by Arnab Kundu
/* C# implementation to delete a doubly Linked List nodeat the given position */using System; // A node of the doubly linked listpublic 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
<script>/* javascript implementation to delete a   doubly Linked List node   at the given position */ // A node of the doubly linked listclass Node {        constructor() {            this.data = 0;            this.prev = null;            this.next = null;        }    }var head = null;     // Function to delete a node    // in a Doubly Linked List.    // head_ref --> pointer to head node pointer.    // del --> pointer to node to be deleted.    function deleteNode(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    function deleteNodeAtGivenPos(n) {        /*         * if list in NULL or invalid position is given         */        if (head == null || n <= 0)            return; var current = head;        var 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(current);    }     // Function to insert a node    // at the beginning of the Doubly Linked List    function push(new_data) {        // allocate nodevar 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;    }     // Function to print nodes in a    // given doubly linked list    function printList() {var temp = head;        if (temp == null)            document.write("Doubly Linked list empty");         while (temp != null) {            document.write(temp.data + " ");            temp = temp.next;        }        document.write();    }     // Driver code             // Create the doubly linked list:        // 10<->8<->4<->2<->5         push(5);        push(2);        push(4);        push(8);        push(10);         document.write("Doubly linked " + "list before deletion:<br/>");        printList();         var n = 2;         // delete node at the given position 'n'        deleteNodeAtGivenPos(n);        document.write("<br/>Doubly linked " + "list after deletion:<br/>");        printList(); // This code contributed by gauravrajput1</script>
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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