Delete all occurrences of a given key in a doubly linked list
Last Updated :
20 Jan, 2023
Given a doubly linked list and a key x. The problem is to delete all occurrences of the given key x from the doubly linked list.
Examples:
Algorithm:
delAllOccurOfGivenKey(head_ref, x)
if head_ref == NULL
return
Initialize current = head_ref
Declare next
while current != NULL
if current->data == x
next = current->next
deleteNode(head_ref, current)
current = next
else
current = current->next
The algorithm for deleteNode(head_ref, current) (which deletes the node using the pointer to the node) is discussed in this post.
Implementation:
C++
/* C++ implementation to delete all occurrences
of a given key in a doubly linked list */
#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 all occurrences of the given
key 'x' */
void deleteAllOccurOfX(struct Node** head_ref, int x)
{
/* if list is empty */
if ((*head_ref) == NULL)
return;
struct Node* current = *head_ref;
struct Node* next;
/* traverse the list up to the end */
while (current != NULL) {
/* if node found with the value 'x' */
if (current->data == x) {
/* save current's next node in the
pointer 'next' */
next = current->next;
/* delete the node pointed to by
'current' */
deleteNode(head_ref, current);
/* update current */
current = next;
}
/* else simply move to the next node */
else
current = current->next;
}
}
/* 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 of 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)
{
/* if list is empty */
if (head == NULL)
cout << "Doubly Linked list empty";
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:
2<->2<->10<->8<->4<->2<->5<->2 */
push(&head, 2);
push(&head, 5);
push(&head, 2);
push(&head, 4);
push(&head, 8);
push(&head, 10);
push(&head, 2);
push(&head, 2);
cout << "Original Doubly linked list:n";
printList(head);
int x = 2;
/* delete all occurrences of 'x' */
deleteAllOccurOfX(&head, x);
cout << "\nDoubly linked list after deletion of "
<< x << ":n";
printList(head);
return 0;
}
/* Java implementation to delete all occurrences
of a given key in a doubly linked list */
import java.util.*;
import java.io.*;
// 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 all occurrences of the given
key 'x' */
static Node deleteAllOccurOfX(Node head, int x)
{
// if list is empty
if (head == null)
return null;
Node current = head;
Node next;
/* traverse the list up to the end */
while (current != null)
{
// if node found with the value 'x'
if (current.data == x)
{
/* save current's next node in the
pointer 'next' */
next = current.next;
/* delete the node pointed to by
'current' */
head = deleteNode(head, current);
/* update current */
current = next;
}
/* else simply move to the next node */
else
current = current.next;
}
return head;
}
/* 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 of 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;
}
}
// 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, 2);
head = push(head, 4);
head = push(head, 8);
head = push(head, 10);
head = push(head, 2);
head = push(head, 2);
System.out.println("Original Doubly linked list: ");
printList(head);
int x = 2;
// delete all occurrences of 'x'
head = deleteAllOccurOfX(head, x);
System.out.println("\nDoubly linked list after deletion of" + x +":");
printList(head);
}
}
// This code is contributed by rachana soma
# Python3 implementation to delete all occurrences
# of a given key in a doubly linked list
import math
# a node of the doubly linked list
class 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, delete):
# base case
if (head == None or delete == None):
return None
# If node to be deleted is head node
if (head == delete):
head = delete.next
# Change next only if node to be deleted
# is NOT the last node
if (delete.next != None):
delete.next.prev = delete.prev
# Change prev only if node to be deleted
# is NOT the first node
if (delete.prev != None):
delete.prev.next = delete.next
# Finally, free the memory occupied by del
# free(del)
delete = None
return head
# function to delete all occurrences of the given
# key 'x'
def deleteAllOccurOfX(head, x):
# if list is empty
if (head == None):
return
current = head
# traverse the list up to the end
while (current != None):
# if node found with the value 'x'
if (current.data == x):
# save current's next node in the
#pointer 'next'
next = current.next
# delete the node pointed to by
# 'current'
head = deleteNode(head, current)
# update current
current = next
# else simply move to the next node
else:
current = current.next
return head
# Function to insert a node at the beginning
# of the Doubly Linked List
def push(head,new_data):
# allocate node
new_node = Node(new_data)
# 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 of the new node
new_node.next = head
# change prev of head node to new node
if (head != None):
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
def printList(head):
# if list is empty
if (head == None):
print("Doubly Linked list empty")
while (head != None) :
print(head.data,end=" ")
head = head.next
# Driver functions
if __name__=='__main__':
# Start with the empty list
head = None
# Create the doubly linked list:
# 2<->2<->10<->8<->4<->2<->5<->2
head = push(head, 2)
head = push(head, 5)
head = push(head, 2)
head = push(head, 4)
head = push(head, 8)
head = push(head, 10)
head = push(head, 2)
head = push(head, 2)
print("Original Doubly linked list:")
printList(head)
x = 2
# delete all occurrences of 'x'
head = deleteAllOccurOfX(head, x)
print("\nDoubly linked list after deletion of ",x,":")
printList(head)
# This article contributed by Srathore
/* C# implementation to delete all occurrences
of a given key in a doubly linked list */
using System;
using System.Collections;
// 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 all occurrences of the given
key 'x' */
static Node deleteAllOccurOfX(Node head, int x)
{
// if list is empty
if (head == null)
return null;
Node current = head;
Node next;
/* traverse the list up to the end */
while (current != null)
{
// if node found with the value 'x'
if (current.data == x)
{
/* save current's next node in the
pointer 'next' */
next = current.next;
/* delete the node pointed to by
'current' */
head = deleteNode(head, current);
/* update current */
current = next;
}
/* else simply move to the next node */
else
current = current.next;
}
return head;
}
/* 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 of 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;
}
}
// 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, 2);
head = push(head, 4);
head = push(head, 8);
head = push(head, 10);
head = push(head, 2);
head = push(head, 2);
Console.WriteLine("Original Doubly linked list: ");
printList(head);
int x = 2;
// delete all occurrences of 'x'
head = deleteAllOccurOfX(head, x);
Console.WriteLine("\nDoubly linked list after deletion of" + x +":");
printList(head);
}
}
// This code is contributed by Arnab Kundu
<script>
/* javascript implementation to delete all occurrences
of a given key in a doubly linked list */
// a node of the doubly linked list
class Node {
constructor(val) {
this.data = val;
this.prev = null;
this.next = 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(head, 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 all occurrences of the given key 'x'
*/
function deleteAllOccurOfX(head , x) {
// if list is empty
if (head == null)
return null;
var current = head;
var next;
/* traverse the list up to the end */
while (current != null) {
// if node found with the value 'x'
if (current.data == x) {
/*
* save current's next node in the pointer 'next'
*/
next = current.next;
/*
* delete the node pointed to by 'current'
*/
head = deleteNode(head, current);
/* update current */
current = next;
}
/* else simply move to the next node */
else
current = current.next;
}
return head;
}
/*
* Function to insert a node at the beginning of the Doubly Linked List
*/
function push(head , new_data) {
// allocate node
var 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 of 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
*/
function printList(temp) {
if (temp == null)
document.write("Doubly Linked list empty");
while (temp != null) {
document.write(temp.data + " ");
temp = temp.next;
}
}
// Driver code
// Start with the empty list
var 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, 2);
head = push(head, 4);
head = push(head, 8);
head = push(head, 10);
head = push(head, 2);
head = push(head, 2);
document.write("Original Doubly linked list: <br/>");
printList(head);
var x = 2;
// delete all occurrences of 'x'
head = deleteAllOccurOfX(head, x);
document.write("<br/>Doubly linked list after deletion of " + x + " :<br/>");
printList(head);
// This code contributed by gauravrajput1
</script>
OutputOriginal Doubly linked list:n2 2 10 8 4 2 5 2
Doubly linked list after deletion of 2:n10 8 4 5
Time Complexity: O(n)
Auxiliary Space: O(1) because no extra space is required
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