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         copyNext(head);
15         copyRandom(head);
16         RandomListNode newHead = splitList(head);
17         return newHead;
18     }
19     
20     private void copyNext(RandomListNode head) {
21         while(head != null) {
22             RandomListNode copy = new RandomListNode(head.label);
23             copy.next = head.next;
24             head.next = copy;
25             head = head.next.next;
26         }
27     }
28     
29     private void copyRandom(RandomListNode head) {
30         while (head != null) {
31             if (head.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             head = head.next;
44             if (temp.next != null) {
45                 temp.next = temp.next.next;
46             }
47         }
48         return newHead;
49     }
50 }