Given an XOR linked list, the task is to remove the first node of the XOR linked list.
Examples:
Input: XLL = 4 < – > 7 < – > 9 < – > 7
Output: 7 < – > 9 < – > 7
Explanation: Removing the first node of the XOR linked list modifies XLL to 7 < – > 9 < – > 7Input: XLL = NULL
Output: List Is Empty
Approach: The idea is to update the head node of the XOR linked list to the second node of the XOR linked list and delete memory allocated for the first node. Follow the steps below to solve the problem:
- Check if the XOR linked list is empty or not. If found to be true, then print “List Is Empty”.
- Otherwise, update the head node of the XOR linked list to the second node of the linked list.
- Delete the first node from memory.
Below is the implementation of the above approach:
C
// C program to implement// the above approach#include <inttypes.h>#include <stdio.h>#include <stdlib.h>// Structure of a node// in XOR linked liststruct Node { // Stores data value // of a node int data; // Stores XOR of previous // pointer and next pointer struct Node* nxp;};// Function to find the XOR// of address two nodesstruct Node* XOR(struct Node* a, struct Node* b){ return (struct Node*)((uintptr_t)(a) ^ (uintptr_t)(b));}// Function to insert a node with// given value at given positionstruct Node* insert(struct Node** head, int value){ // Check If XOR linked list // is empty if (*head == NULL) { // Initialize a new Node struct Node* node = (struct Node*)malloc(sizeof(struct Node)); // Stores data value in // the node node->data = value; // Stores XOR of previous // and next pointer node->nxp = XOR(NULL, NULL); // Update pointer of head node *head = node; } // If the XOR linked list // is not empty else { // Stores the address // of current node struct Node* curr = *head; // Stores the address // of previous node struct Node* prev = NULL; // Initialize a new Node struct Node* node = (struct Node*)malloc( sizeof(struct Node)); // Update curr node address curr->nxp = XOR(node, XOR(NULL, curr->nxp)); // Update new node address node->nxp = XOR(NULL, curr); // Update head *head = node; // Update data value of // current node node->data = value; } return *head;}// Function to print elements of// the XOR Linked Listvoid printList(struct Node** head){ // Stores XOR pointer // in current node struct Node* curr = *head; // Stores XOR pointer of // in previous Node struct Node* prev = NULL; // Stores XOR pointer of // in next node struct Node* next; // Traverse XOR linked list while (curr != NULL) { // Print current node printf("%d ", curr->data); // Forward traversal next = XOR(prev, curr->nxp); // Update prev prev = curr; // Update curr curr = next; }}// Function to remove the first node from// the given linked liststruct Node* delBeginning(struct Node** head){ // If list is empty if (*head == NULL) printf("List Is Empty"); else { // Store the node to be deleted struct Node* temp = *head; // Update the head pointer *head = XOR(NULL, temp->nxp); // When the linked list // contains only one node if (*head != NULL) { // Update head node address (*head)->nxp = XOR(NULL, XOR(temp, (*head)->nxp)); } free(temp); } return *head;}// Driver Codeint main(){ /* Create following XOR Linked List head-->40<-->30<-->20<-->10 */ struct Node* head = NULL; insert(&head, 10); insert(&head, 20); insert(&head, 30); insert(&head, 40); // Delete the first node delBeginning(&head); /* Print the following XOR Linked List head-->30<-->20<-->10 */ printList(&head); return (0);} |
C++
#include <iostream>#include <cstdlib>using namespace std;// Structure of a node in XOR linked liststruct Node { int data; struct Node* nxp;};// Function to find the XOR of address two nodesstruct Node* XOR(struct Node* a, struct Node* b){ return (struct Node*)((uintptr_t)(a) ^ (uintptr_t)(b));}// Function to insert a node with given value at given positionstruct Node* insert(struct Node** head, int value){ // Check If XOR linked list is empty if (*head == NULL) { // Initialize a new Node struct Node* node = (struct Node*)malloc(sizeof(struct Node)); // Stores data value in the node node->data = value; // Stores XOR of previous and next pointer node->nxp = XOR(NULL, NULL); // Update pointer of head node *head = node; } // If the XOR linked list is not empty else { // Stores the address of current node struct Node* curr = *head; // Stores the address of previous node struct Node* prev = NULL; // Initialize a new Node struct Node* node = (struct Node*)malloc(sizeof(struct Node)); // Update curr node address curr->nxp = XOR(node, XOR(NULL, curr->nxp)); // Update new node address node->nxp = XOR(NULL, curr); // Update head *head = node; // Update data value of current node node->data = value; } return *head;}// Function to print elements of the XOR Linked Listvoid printList(struct Node** head){ // Stores XOR pointer in current node struct Node* curr = *head; // Stores XOR pointer of in previous Node struct Node* prev = NULL; // Stores XOR pointer of in next node struct Node* next; // Traverse XOR linked list while (curr != NULL) { // Print current node cout << curr->data << " "; // Forward traversal next = XOR(prev, curr->nxp); // Update prev prev = curr; // Update curr curr = next; }}// Function to remove the first node from the given linked liststruct Node* delBeginning(struct Node** head){ // If list is empty if (*head == NULL) cout << "List Is Empty"; else { // Store the node to be deleted struct Node* temp = *head; // Update the head pointer *head = XOR(NULL, temp->nxp); // When the linked list contains only one node if (*head != NULL) { // Update head node address (*head)->nxp = XOR(NULL, XOR(temp, (*head)->nxp)); } free(temp); } return *head;}int main(){ /* Create following XOR Linked Listhead-->40<-->30<-->20<-->10 */struct Node* head = NULL;insert(&head, 10);insert(&head, 20);insert(&head, 30);insert(&head, 40);// Delete the first nodedelBeginning(&head);/* Print the following XOR Linked Listhead-->30<-->20<-->10 */printList(&head);return (0);}// This code is contributed by lokeshpotta20. |
Java
import java.util.HashMap;import java.util.Map;class Node { int data; int npx; Node(int data) { this.data = data; this.npx = 0; }}class XorLinkedList { Node head; Node[] nodes; XorLinkedList() { head = null; nodes = new Node[100]; // assuming 100 as max number of nodes } void insert(int data) { Node node = new Node(data); nodes[data - 1] = node; // assuming data starts from 1 and is unique if (head != null) { node.npx = getPointer(head); head.npx = getPointer(node) ^ head.npx; } head = node; } void removeHead() { if (head == null) { System.out.println("List Is Empty"); return; } int nextNodeId = head.npx; if (nextNodeId != 0) { Node nextNode = dereferencePointer(nextNodeId); nextNode.npx ^= getPointer(head); nodes[head.data - 1] = null; // removing head node from nodes array head = nextNode; } } void printList() { Node current = head; int prevAddr = 0; while (current != null) { System.out.println(current.data); int nextAddr = prevAddr ^ current.npx; prevAddr = getPointer(current); current = dereferencePointer(nextAddr); } } int getPointer(Node node) { // Using System.identityHashCode to get a unique identifier for the node object return System.identityHashCode(node); } Node dereferencePointer(int address) { for (int i = 0; i < nodes.length; i++) { if (nodes[i] != null && getPointer(nodes[i]) == address) { return nodes[i]; } } return null; }}public class Main { public static void main(String[] args) { XorLinkedList xll = new XorLinkedList(); xll.insert(10); xll.insert(20); xll.insert(30); xll.insert(40); xll.removeHead(); xll.printList(); }} |
Python3
import ctypes# Structure of a node in XOR linked listclass Node: def __init__(self, value): self.value = value self.npx = 0# create linked list classclass XorLinkedList: # constructor def __init__(self): self.head = None self.tail = None self.__nodes = [] # Function to insert a node with given value at given position def insert(self, value): # Initialize a new Node node = Node(value) # Check If XOR linked list is empty if self.head is None: # Update pointer of head node self.head = node # Update pointer of tail node self.tail = node else: # Update curr node address self.head.npx = id(node) ^ self.head.npx # Update new node address node.npx = id(self.head) # Update head self.head = node # push node self.__nodes.append(node) # Function to print elements of the XOR Linked List def printList(self): if self.head != None: prev_id = 0 node = self.head next_id = 1 print(node.value, end=' ') # Traverse XOR linked list while next_id: # Forward traversal next_id = prev_id ^ node.npx if next_id: # Update prev prev_id = id(node) # Update curr node = self.__type_cast(next_id) # Print current node print(node.value, end=' ') else: return # method to check if the linked list is empty or not def isEmpty(self): if self.head is None: return True return False # method to return a new instance of type def __type_cast(self, id): return ctypes.cast(id, ctypes.py_object).value # Function to remove the first node from the given linked list def delBeginning(self): # If list is empty if self.isEmpty(): return "List is empty !" # If list has 1 node elif self.head == self.tail: self.head = self.tail = None # If list has 2 nodes elif (0 ^ self.head.npx) == id(self.tail): self.head = self.tail self.head.npx = self.tail.npx = 0 # If list has more than 2 nodes else: # Store the node to be deleted res = self.head.value # Address of next node x = self.__type_cast(0 ^ self.head.npx) # Address of next of next node y = (id(self.head) ^ x.npx) self.head = x self.head.npx = 0 ^ y return res # Create following XOR Linked List# head-->40<-->30<-->20<-->10 head = XorLinkedList()head.insert(10)head.insert(20)head.insert(30)head.insert(40)# Delete the first nodehead.delBeginning();# Print the following XOR Linked List# head-->30<-->20<-->10 head.printList();# This code is contributed by Nighi goel. |
C#
using System;class Node { public int data; public int npx; public Node(int data) { this.data = data; this.npx = 0; }}class XorLinkedList { private Node head; private Node[] nodes; public XorLinkedList() { head = null; nodes = new Node[100]; // assuming 100 as max number of nodes } public void insert(int data) { Node node = new Node(data); nodes[data - 1] = node; // assuming data starts from 1 and is unique if (head != null) { node.npx = getPointer(head); head.npx = getPointer(node) ^ head.npx; } head = node; } public void removeHead() { if (head == null) { Console.WriteLine("List Is Empty"); return; } int nextNodeId = head.npx; if (nextNodeId != 0) { Node nextNode = dereferencePointer(nextNodeId); nextNode.npx ^= getPointer(head); nodes[head.data - 1] = null; // removing head node from nodes array head = nextNode; } } public void printList() { Node current = head; int prevAddr = 0; while (current != null) { Console.WriteLine(current.data); int nextAddr = prevAddr ^ current.npx; prevAddr = getPointer(current); current = dereferencePointer(nextAddr); } } private int getPointer(Node node) { // Using RuntimeHelpers.GetHashCode to get a unique identifier for the node object return System.Runtime.CompilerServices.RuntimeHelpers.GetHashCode(node); } private Node dereferencePointer(int address) { for (int i = 0; i < nodes.Length; i++) { if (nodes[i] != null && getPointer(nodes[i]) == address) { return nodes[i]; } } return null; }}public class Program { public static void Main() { XorLinkedList xll = new XorLinkedList(); xll.insert(10); xll.insert(20); xll.insert(30); xll.insert(40); xll.removeHead(); xll.printList(); }} |
Javascript
class Node { constructor(data) { this.data = data; this.npx = 0; }}class XorLinkedList { constructor() { this.head = null; this.nodes = []; } insert(data) { let node = new Node(data); this.nodes.push(node); if (this.head !== null) { node.npx = getPointer(this.head); this.head.npx = getPointer(node) ^ this.head.npx; } this.head = node; } removeHead() { if (!this.head) { console.log("List Is Empty"); return; } let nextNodeId = this.head.npx; if (nextNodeId !== 0) { let nextNode = dereferencePointer(nextNodeId); nextNode.npx ^= getPointer(this.head); delete this.nodes[this.nodes.indexOf(this.head)]; delete this.head; this.head = nextNode; } } printList() { let current = this.head; let prevAddr = 0; while (current != null) { console.log(current.data); let nextAddr = prevAddr ^ current.npx; prevAddr = getPointer(current); current = dereferencePointer(nextAddr); } }}let addressMap = new Map();let addressCount = 1;function getPointer(object) { if (addressMap.has(object)) return addressMap.get(object); let newAddressCountValue = addressCount++; addressMap.set(object, newAddressCountValue); return newAddressCountValue;}function dereferencePointer(address) { for (let [key, value] of addressMap.entries()) { if (value === address) return key; } return undefined}let xll = new XorLinkedList();xll.insert(10);xll.insert(20);xll.insert(30);xll.insert(40);xll.removeHead();xll.printList(); |
Output:
30 20 10
Time Complexity: O(1)
Auxiliary Space: O(1)
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