Clone a Linked List with next and Random Pointer
Given a linked list of size N where each node has two links: one pointer points to the next node and the second pointer points to any node in the list. The task is to create a clone of this linked list in O(N) time.
Note: The pointer pointing to the next node is ‘next‘ pointer and the one pointing to an arbitrary node is called ‘arbit’ pointer as it can point to any arbitrary node in the linked list.
An example of the linked list is shown in the below image:
Clone a Linked List with next and Random Pointer using Extra Space:
First create a single linked list with only the ‘next’ pointer and use a mapping to map the new nodes to their corresponding nodes in the given linked list. Now use this mapping to point the arbitrary node from any node in the newly created list.
Follow the steps mentioned below to implement the above idea:
- Create a duplicate (say Y) for each node (say X) and map them with corresponding old nodes (say mp, So mp[X] = Y).
- Create the single linked list of the duplicate nodes where each node only has the ‘next’ pointer.
- Now iterate over the old linked list and do the following:
- Find the duplicate node mapped with the current one. (i.e., if the current node is X then duplicate is mp[x])
- Make the arbit pointer of the duplicate node pointing to the duplicate of the current->arbit node (i.e., mp[x]->arbit will point to mp[X->arbit]).
- The linked list created in this way is the required linked list.
Follow the illustration below for a better understanding:
Illustration:
Consider the linked list shown below:
The green links are the arbit pointers
Creating copy of Nodes and next pointer:
Initially create single linked list of duplicate nodes with only the next pointers and map them with the old ones.
Here the blue coloured links are used to show the mapping.Linking the arbit pointers:
Now iterating the old array and update the arbit pointers as mentioned in the approach. The green coloured links are the arbit pointers.
At first node:
At second node:
At third node:
At fourth node:
At fifth node:
The final linked list is as shown below:
Below is the implementation of the above approach:
C++14
// C++ code to implement the approach #include <bits/stdc++.h> using namespace std; // Structure of a node of linked list struct Node { int val; Node* next; Node* arbit; // Constructor Node( int x) { this ->val = x; this ->next = NULL; this ->arbit = NULL; } }; // Function to clone the linked list Node* cloneLinkedList(Node* head) { // Map to store the mapping of // old nodes with new ones unordered_map<Node*, Node*> mp; Node *temp, *nhead; // Duplicate of the first node temp = head; nhead = new Node(temp->val); mp[temp] = nhead; // Loop to create duplicates of nodes // with only next pointer while (temp->next != NULL) { nhead->next = new Node(temp->next->val); temp = temp->next; nhead = nhead->next; mp[temp] = nhead; } temp = head; // Loop to clone the arbit pointers while (temp != NULL) { mp[temp]->arbit = mp[temp->arbit]; temp = temp->next; } // Return the head of the clone return mp[head]; } // Function to print the linked list void printList(Node* head) { cout << head->val << "(" << head->arbit->val << ")" ; head = head->next; while (head != NULL) { cout << " -> " << head->val << "(" << head->arbit->val << ")" ; head = head->next; } cout << endl; } // Driver code int main() { // Creating a linked list with random pointer Node* head = new Node(1); head->next = new Node(2); head->next->next = new Node(3); head->next->next->next = new Node(4); head->next->next->next->next = new Node(5); head->arbit = head->next->next; head->next->arbit = head; head->next->next->arbit = head->next->next->next->next; head->next->next->next->arbit = head->next->next; head->next->next->next->next->arbit = head->next; // Print the original list cout << "The original linked list:\n" ; printList(head); // Function call Node* sol = cloneLinkedList(head); cout << "The cloned linked list:\n" ; printList(sol); return 0; } |
Java
// Java code to implement the approach import java.io.*; import java.util.HashMap; class Node { int val; Node next; Node arbit; // Constructor Node( int x) { this .val = x; this .next = null ; this .arbit = null ; } } class GFG { static Node cloneLinkedList(Node head) { // Map to store the mapping of // old nodes with new ones HashMap<Node, Node> mp = new HashMap<>(); Node temp, nhead; // Duplicate of the first node temp = head; nhead = new Node(temp.val); mp.put(temp, nhead); // Loop to create duplicates of nodes // with only next pointer while (temp.next != null ) { nhead.next = new Node(temp.next.val); temp = temp.next; nhead = nhead.next; mp.put(temp, nhead); } temp = head; // Loop to clone the arbit pointers while (temp != null ) { mp.get(temp).arbit = mp.get(temp.arbit); temp = temp.next; } // Return the head of the clone return mp.get(head); } static void printList(Node head) { System.out.print(head.val + "(" + head.arbit.val + ")" ); head = head.next; while (head != null ) { System.out.print( " -> " + head.val + "(" + head.arbit.val + ")" ); head = head.next; } System.out.println(); } public static void main(String[] args) { // Creating a linked list with random pointer Node head = new Node( 1 ); head.next = new Node( 2 ); head.next.next = new Node( 3 ); head.next.next.next = new Node( 4 ); head.next.next.next.next = new Node( 5 ); head.arbit = head.next.next; head.next.arbit = head; head.next.next.arbit = head.next.next.next.next; head.next.next.next.arbit = head.next.next; head.next.next.next.next.arbit = head.next; // Print the original list System.out.println( "The original linked list:" ); printList(head); // Function call Node sol = cloneLinkedList(head); System.out.println( "The cloned linked list:" ); printList(sol); } } /// This code is contributed by lokesh. |
Python3
# Structure of a node of linked list class Node: def __init__( self , val): self .val = val self . next = None self .arbit = None # Function to clone the linked list def cloneLinkedList(head): # Map to store the mapping of # old nodes with new ones mp = {} temp = head nhead = Node(temp.val) mp[temp] = nhead # Loop to create duplicates of nodes # with only next pointer while temp. next : nhead. next = Node(temp. next .val) temp = temp. next nhead = nhead. next mp[temp] = nhead temp = head # Loop to clone the arbit pointers while temp: mp[temp].arbit = mp[temp.arbit] temp = temp. next # Return the head of the clone return mp[head] # Function to print the linked list def printList(head): result = [] while head: result.append(f "{head.val}({head.arbit.val})" ) head = head. next print ( " -> " .join(result)) # Creating a linked list with random pointer head = Node( 1 ) head. next = Node( 2 ) head. next . next = Node( 3 ) head. next . next . next = Node( 4 ) head. next . next . next . next = Node( 5 ) head.arbit = head. next . next head. next .arbit = head head. next . next .arbit = head. next . next . next . next head. next . next . next .arbit = head. next . next head. next . next . next . next .arbit = head. next # Print the original list print ( "The original linked list:" ) printList(head) # Function call sol = cloneLinkedList(head) print ( "The cloned linked list:" ) printList(sol) |
C#
// C# code to implement the approach using System; using System.Collections.Generic; class Node { public int val; public Node next; public Node arbit; // Constructor public Node( int x) { this .val = x; this .next = null ; this .arbit = null ; } } public class GFG { static Node cloneLinkedList(Node head) { // Map to store the mapping of // old nodes with new ones Dictionary<Node, Node> mp = new Dictionary<Node, Node>(); Node temp, nhead; // Duplicate of the first node temp = head; nhead = new Node(temp.val); mp[temp] = nhead; // Loop to create duplicates of nodes // with only next pointer while (temp.next != null ) { nhead.next = new Node(temp.next.val); temp = temp.next; nhead = nhead.next; mp[temp] = nhead; } temp = head; // Loop to clone the arbit pointers while (temp != null ) { mp[temp].arbit = mp[temp.arbit]; temp = temp.next; } // Return the head of the clone return mp[head]; } static void printList(Node head) { Console.Write(head.val + "(" + head.arbit.val + ")" ); head = head.next; while (head != null ) { Console.Write( " -> " + head.val + "(" + head.arbit.val + ")" ); head = head.next; } Console.WriteLine(); } static public void Main() { // Code // Creating a linked list with random pointer Node head = new Node(1); head.next = new Node(2); head.next.next = new Node(3); head.next.next.next = new Node(4); head.next.next.next.next = new Node(5); head.arbit = head.next.next; head.next.arbit = head; head.next.next.arbit = head.next.next.next.next; head.next.next.next.arbit = head.next.next; head.next.next.next.next.arbit = head.next; // Print the original list Console.WriteLine( "The original linked list:" ); printList(head); // Function call Node sol = cloneLinkedList(head); Console.WriteLine( "The cloned linked list:" ); printList(sol); } } // This code is contributed by lokeshmvs21. |
Javascript
// Javascript code to implement the approach class Node { constructor(val) { this .val = val; this .next = null ; this .arbit = null ; } } const cloneLinkedList = (head) => { // Map to store the mapping of old nodes with new ones const mp = new Map(); let temp = head; let nhead = new Node(temp.val); mp.set(temp, nhead); // Loop to create duplicates of nodes with only next pointer while (temp.next) { nhead.next = new Node(temp.next.val); temp = temp.next; nhead = nhead.next; mp.set(temp, nhead); } temp = head; // Loop to clone the arbit pointers while (temp) { mp.get(temp).arbit = mp.get(temp.arbit); temp = temp.next; } // Return the head of the clone return mp.get(head); } const printList = (head) => { let str = `${head.val}(${head.arbit.val})`; head = head.next; while (head) { str += ` -> ${head.val}(${head.arbit.val})`; head = head.next; } console.log(str); } // Creating a linked list with random pointer const head = new Node(1); head.next = new Node(2); head.next.next = new Node(3); head.next.next.next = new Node(4); head.next.next.next.next = new Node(5); head.arbit = head.next.next; head.next.arbit = head; head.next.next.arbit = head.next.next.next.next; head.next.next.next.arbit = head.next.next; head.next.next.next.next.arbit = head.next; // Print the original list console.log( "The original linked list:" ); printList(head); // Function call const sol = cloneLinkedList(head); console.log( "The cloned linked list:" ); printList(sol); // This code is contributed by shivamsharma215 |
The original linked list: 1(3) -> 2(1) -> 3(5) -> 4(3) -> 5(2) The cloned linked list: 1(3) -> 2(1) -> 3(5) -> 4(3) -> 5(2)
Time Complexity: O(N)
Auxiliary Space: O(N)
Clone a Linked List with next and Random Pointer without using any Extra Space:
Create duplicate of a node and insert it in between that node and the node just next to it.
Now for a node X its duplicate will be X->next and the arbitrary pointer of the duplicate will point to X->arbit->next [as that is the duplicate of X->arbit]
Follow the steps mentioned below to implement the idea:
- Create the copy of node 1 and insert it between node 1 and node 2 in the original Linked List, create the copy of node 2 and insert it between 2nd and 3rd node and so on. Add the copy of N after the Nth node
- Now copy the arbitrary link in this fashion:
original->next->arbitrary = original->arbitrary->next
- Now restore the original and copy linked lists in this fashion in a single loop.
original->next = original->next->next;
copy->next = copy->next->next;
- Make sure that the last element of original->next is NULL.
C++
// C++ code to implement the approach #include <bits/stdc++.h> using namespace std; struct Node { int data; Node *next, *random; Node( int x) { data = x; next = random = NULL; } }; Node* cloneLinkedList(Node* head) { if (head == NULL) { return NULL; } // Step 1: Create new nodes and insert them next to the original nodes Node* curr = head; while (curr != NULL) { Node* newNode = new Node(curr->data); newNode->next = curr->next; curr->next = newNode; curr = newNode->next; } // Step 2: Set the random pointers of the new nodes curr = head; while (curr != NULL) { if (curr->random != NULL) { curr->next->random = curr->random->next; } curr = curr->next->next; } // Step 3: Separate the new nodes from the original nodes curr = head; Node* clonedHead = head->next; Node* clonedCurr = clonedHead; while (clonedCurr->next != NULL) { curr->next = curr->next->next; clonedCurr->next = clonedCurr->next->next; curr = curr->next; clonedCurr = clonedCurr->next; } curr->next = NULL; clonedCurr->next = NULL; return clonedHead; } // Function to print the linked list void printList(Node* head) { cout << head->data << "(" << head->random->data << ")" ; head = head->next; while (head != NULL) { cout << " -> " << head->data << "(" << head->random->data << ")" ; head = head->next; } cout << endl; } // Driver code int main() { // Creating a linked list with random pointer Node* head = new Node(1); head->next = new Node(2); head->next->next = new Node(3); head->next->next->next = new Node(4); head->next->next->next->next = new Node(5); head->random = head->next->next; head->next->random = head; head->next->next->random = head->next->next->next->next; head->next->next->next->random = head->next->next; head->next->next->next->next->random = head->next; // Print the original list cout << "The original linked list:\n" ; printList(head); // Function call Node* sol = cloneLinkedList(head); cout << "The cloned linked list:\n" ; printList(sol); return 0; } |
Java
class Node { int data; Node next, random; Node( int x) { data = x; next = random = null ; } } public class Main { public static void main(String[] args) { // Creating a linked list with random pointer Node head = new Node( 1 ); head.next = new Node( 2 ); head.next.next = new Node( 3 ); head.next.next.next = new Node( 4 ); head.next.next.next.next = new Node( 5 ); head.random = head.next.next; head.next.random = head; head.next.next.random = head.next.next.next.next; head.next.next.next.random = head.next.next; head.next.next.next.next.random = head.next; // Print the original list System.out.println( "The original linked list:" ); printList(head); // Function call Node sol = cloneLinkedList(head); System.out.println( "The cloned linked list:" ); printList(sol); } public static Node cloneLinkedList(Node head) { if (head == null ) { return null ; } // Step 1: Create new nodes and insert them next to the original nodes Node curr = head; while (curr != null ) { Node newNode = new Node(curr.data); newNode.next = curr.next; curr.next = newNode; curr = newNode.next; } // Step 2: Set the random pointers of the new nodes curr = head; while (curr != null ) { if (curr.random != null ) { curr.next.random = curr.random.next; } curr = curr.next.next; } // Step 3: Separate the new nodes from the original nodes curr = head; Node clonedHead = head.next; Node clonedCurr = clonedHead; while (clonedCurr.next != null ) { curr.next = curr.next.next; clonedCurr.next = clonedCurr.next.next; curr = curr.next; clonedCurr = clonedCurr.next; } curr.next = null ; clonedCurr.next = null ; return clonedHead; } // Function to print the linked list public static void printList(Node head) { System.out.print(head.data + "(" + head.random.data + ")" ); head = head.next; while (head != null ) { System.out.print( " -> " + head.data + "(" + head.random.data + ")" ); head = head.next; } System.out.println(); } } |
Python3
class Node: def __init__( self , x): self .data = x self . next = None self .random = None def cloneLinkedList(head): if head = = None : return None # Step 1: Create new nodes and insert them next to the original nodes curr = head while curr ! = None : newNode = Node(curr.data) newNode. next = curr. next curr. next = newNode curr = newNode. next # Step 2: Set the random pointers of the new nodes curr = head while curr ! = None : if curr.random ! = None : curr. next .random = curr.random. next curr = curr. next . next # Step 3: Separate the new nodes from the original nodes curr = head clonedHead = head. next clonedCurr = clonedHead while clonedCurr. next ! = None : curr. next = curr. next . next clonedCurr. next = clonedCurr. next . next curr = curr. next clonedCurr = clonedCurr. next curr. next = None clonedCurr. next = None return clonedHead # Function to print the linked list def printList(head): print (head.data, "(" , head.random.data, ")" , end = "") head = head. next while head ! = None : print ( "->" , head.data, "(" , head.random.data, ")" , end = "") head = head. next print () # Driver code if __name__ = = '__main__' : # Creating a linked list with random pointer head = Node( 1 ) head. next = Node( 2 ) head. next . next = Node( 3 ) head. next . next . next = Node( 4 ) head. next . next . next . next = Node( 5 ) head.random = head. next . next head. next .random = head head. next . next .random = head. next . next . next . next head. next . next . next .random = head. next . next head. next . next . next . next .random = head. next # Print the original list print ( "The original linked list:" ) printList(head) # Function call sol = cloneLinkedList(head) print ( "The cloned linked list:" ) printList(sol) |
C#
using System; public class Node { public int data; public Node next, random; public Node( int x) { data = x; next = random = null ; } } public class GFG { public static Node CloneLinkedList(Node head) { if (head == null ) { return null ; } // Step 1: Create new nodes and insert them next to the original nodes Node curr = head; while (curr != null ) { Node newNode = new Node(curr.data); newNode.next = curr.next; curr.next = newNode; curr = newNode.next; } // Step 2: Set the random pointers of the new nodes curr = head; while (curr != null ) { if (curr.random != null ) { curr.next.random = curr.random.next; } curr = curr.next.next; } // Step 3: Separate the new nodes from the original nodes curr = head; Node clonedHead = head.next; Node clonedCurr = clonedHead; while (clonedCurr.next != null ) { curr.next = curr.next.next; clonedCurr.next = clonedCurr.next.next; curr = curr.next; clonedCurr = clonedCurr.next; } curr.next = null ; clonedCurr.next = null ; return clonedHead; } // Function to print the linked list public static void PrintList(Node head) { Console.Write(head.data + "(" + head.random.data + ")" ); head = head.next; while (head != null ) { Console.Write( " -> " + head.data + "(" + head.random.data + ")" ); head = head.next; } Console.WriteLine(); } public static void Main() { // Creating a linked list with random pointer Node head = new Node(1); head.next = new Node(2); head.next.next = new Node(3); head.next.next.next = new Node(4); head.next.next.next.next = new Node(5); head.random = head.next.next; head.next.random = head; head.next.next.random = head.next.next.next.next; head.next.next.next.random = head.next.next; head.next.next.next.next.random = head.next; // Print the original list Console.WriteLine( "The original linked list:" ); PrintList(head); // Function call Node sol = CloneLinkedList(head); Console.WriteLine( "The cloned linked list:" ); PrintList(sol); } } |
Javascript
// JavaScript code to implement the approach class Node { constructor(x) { this .data = x; this .next = null ; this .random = null ; } } function cloneLinkedList(head) { if (head === null ) { return null ; } // Step 1: Create new nodes and insert them next to the original nodes let curr = head; while (curr !== null ) { const newNode = new Node(curr.data); newNode.next = curr.next; curr.next = newNode; curr = newNode.next; } // Step 2: Set the random pointers of the new nodes curr = head; while (curr !== null ) { if (curr.random !== null ) { curr.next.random = curr.random.next; } curr = curr.next.next; } // Step 3: Separate the new nodes from the original nodes curr = head; const clonedHead = head.next; let clonedCurr = clonedHead; while (clonedCurr.next !== null ) { curr.next = curr.next.next; clonedCurr.next = clonedCurr.next.next; curr = curr.next; clonedCurr = clonedCurr.next; } curr.next = null ; clonedCurr.next = null ; return clonedHead; } // Function to print the linked list function printList(head) { process.stdout.write(head.data + "(" + (head.random.data + ")" )); head = head.next; while (head !== null ) { process.stdout.write( " -> " + head.data + "(" + (head.random.data + ")" )); head = head.next; } console.log(); } // Driver code // Creating a linked list with random pointer const head = new Node(1); head.next = new Node(2); head.next.next = new Node(3); head.next.next.next = new Node(4); head.next.next.next.next = new Node(5); head.random = head.next.next; head.next.random = head; head.next.next.random = head.next.next.next.next; head.next.next.next.random = head.next.next; head.next.next.next.next.random = head.next; // Print the original list console.log( "The original linked list:" ); printList(head); // Function call const sol = cloneLinkedList(head); console.log( "The cloned linked list:" ); printList(sol); // The code is contributed by Arushi Goel. |
The original linked list: 1(3) -> 2(1) -> 3(5) -> 4(3) -> 5(2) The cloned linked list: 1(3) -> 2(1) -> 3(5) -> 4(3) -> 5(2)
Time Complexity: O(N)
Auxiliary Space: O(1)
Related article:
Clone a linked list with next and random pointer | Set 2
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