Copy List with Random Pointer.java

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.

/**
 * Definition for singly-linked list with a random pointer.
 * class RandomListNode {
 *     int label;
 *     RandomListNode next, random;
 *     RandomListNode(int x) { this.label = x; }
 * };
 */
public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
    	if (head == null) return head;
    	RandomListNode cur = head;
    	while (cur != null) {
    		RandomListNode newNode = new RandomListNode(cur.label);
    		newNode.next = cur.next;
    		cur.next = newNode;
    		cur = newNode.next;
    	}
    	cur = head;
    	while (cur != null) {
    		if (cur.random != null) {
    			cur.next.random = cur.random.next;
    		}
    		cur = cur.next.next;
    	}
    	cur = head.next;
    	RandomListNode newHead = cur;
    	RandomListNode old = head;
    	while (old != null) {
    		old.next = old.next.next;
    		if (old.next != null) {
    			cur.next = old.next.next;
    		}
    		cur = cur.next;
    		old = old.next;
    	}
    	return newHead;
    }
}