CopyRandomList.java

import java.util.HashMap;
import java.util.Random;
public class CopyRandomList {
//    public Node copyRandomList(Node head) {
//        if(head == null) return head;
//        //for having a track of random mapping
//        HashMap<Node,Node> map = new HashMap<>();
//        //creating the duplicate with the start same as head.val
//        Node start = new Node(head.val);
//
//        //making the node1 with head.next val and node2 as with head
//        Node node1 = head.next;
//        Node node2 = start;
//        //having the map of original and creating dup
//        map.put(head,start);
//        while(node1 != null){
//            node2.next = new Node(node1.val);//adding link with next val as node1.val
//            node2 = node2.next;// moving the node to point to next
//            map.put(node1,node2);// updating the map
//            node1 = node1.next;
//        }
//        node1 = head;
//        node2 = start;
//        while(node2 != null){
//            node2.random = map.get(node1.random);
//            node2 = node2.next;
//            node1 = node1.next;
//        }
//        return start;
//    }
}