Copy List with Random Pointer(0138/Medium)

Copy a postings list

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list.

public class PNode<E> {
    public E data;
    public PNode<E> next;
    PNode<E> jump;

    public PNode(E data,PNode<E> next, PNode<E> jump) {
        this.data = data;
        this.next = next;
        this.jump = jump;
    }

    public PNode(E data,PNode<E> next) {
        this.data = data;
        this.next = next;
        this.jump = null;
    }
}

public static PNode<Integer> copyPostingsList(PNode<Integer> L) {
    if (L == null) {
        return null;
    }

    // Stage 1: Makes a copy of the original list without assigning the jump
    //          field, and creates the mapping for each node in the original
    //          list to the copied list.
    PNode<Integer> iter = L;
    while (iter != null) {
        PNode<Integer> newNode = new PNode<>(iter.data, iter.next, null);
        iter.next = newNode;
        iter = newNode.next;
    }

    // Stage 2: Assigns the jump field in the copied list.
    iter = L;
    while (iter != null) {
        if (iter.jump != null) {
            iter.next.jump = iter.jump.next;
        }
        iter = iter.next.next;
    }

    // Stage 3: Reverts the original list, and assigns the next field of
    //          the copied list.
    iter = L;
    PNode<Integer> newListHead = iter.next;
    while (iter != null) {
        PNode<Integer> newNode = iter.next;
        iter.next = newNode.next;
        if(newNode.next!=null) 
           newNode.next = newNode.next.next;  
        iter = iter.next;
    }
    return newListHead;
}