Copy List with Random Pointer

 1 /**
 2  * Definition for singly-linked list with a random pointer.
 3  * class RandomListNode {
 4  *     int label;
 5  *     RandomListNode next, random;
 6  *     RandomListNode(int x) { this.label = x; }
 7  * };
 8  */
 9 public class Solution {
10     public RandomListNode copyRandomList(RandomListNode head) {
11         if (head == null) {
12             return null;
13         }
14         copyList(head);
15         copyRandom(head);
16         return splitList(head);
17     }
18     
19     private void copyList(RandomListNode head) {
20         while (head != null) {
21             RandomListNode newNode = new RandomListNode(head.label);
22             newNode.random = head.random;
23             newNode.next = head.next;
24             head.next = newNode;
25             head = head.next.next;
26         }
27     }
28     
29     private void copyRandom(RandomListNode head) {
30         while (head != null) {
31             if (head.next.random != null) {
32                 head.next.random = head.random.next;
33             }
34             head = head.next.next;
35         }
36     }
37     
38     private RandomListNode splitList(RandomListNode head) {
39         RandomListNode newHead = head.next;
40         while (head != null) {
41             RandomListNode temp = head.next;
42             head.next = temp.next;
43             if (temp.next != null) {
44                 temp.next = temp.next.next;
45             }
46             head = head.next;
47         }
48         return newHead;
49     }
50 }