Clone_a_linked_list_with_next_and_random_pointer.cpp

/*
Problem Statement:
-----------------
You are given a special linked list with N nodes where each node has a next pointer pointing to its next node. You are also given M random pointers , 
where you will be given M number of pairs denoting two nodes a and b  i.e. a->arb = b.

Example 1:
---------
Input:
N = 4, M = 2
value = {1,2,3,4}
pairs = {{1,2},{2,4}}
Output: 1

Explanation: In this test case, there re 4 nodes in linked list. Among these 4 nodes, 2 nodes have arbit pointer set, rest two nodes have arbit pointer
as NULL. Second line tells us the value of four nodes. The third line gives the information about arbitrary pointers. The first node arbit pointer is set to
node 2.  The second node arbit pointer is set to node 4.

Example 2:
---------
Input:
N = 4, M = 2
value[] = {1,3,5,9}
pairs[] = {{1,1},{3,4}}
Output: 1

Explanation: In the given testcase, applying the method as stated in the above example, the output will be 1.

Your Task: The task is to complete the function copyList() which takes one argument the head of the linked list to be cloned and should return the head of the cloned linked list.
NOTE : If their is any node whose arbitrary pointer is not given then its by default null.

Expected Time Complexity : O(n)
Expected Auxilliary Space : O(1)
*/

// Link --> https://practice.geeksforgeeks.org/problems/clone-a-linked-list-with-next-and-random-pointer/1#

// Code:
Node *copyList(Node *head) 
{
    Node *current = head;
    Node *temp;
    while(current != NULL)
    {
        temp = current->next;
        current->next = new Node(current->data);
        current->next->next = temp;
        current = temp;
    }
    
    current = head;
    while(current != NULL)
    {
        current->next->arb = current->arb ? current->arb->next : current->arb;
        current = current->next->next;
    }
    
    Node *originalHead = head;
    Node *copyHead = head->next;
    
    temp = copyHead;
    
    while(originalHead and copyHead)
    {
        originalHead->next = originalHead->next->next;
        copyHead->next = copyHead->next ? copyHead->next->next : copyHead->next;
        originalHead = originalHead->next;
        copyHead = copyHead->next;
    }
    return temp;
}