Leetcode-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         Map<RandomListNode,RandomListNode> map = new HashMap<RandomListNode,RandomListNode>();
12         if (head==null) return null;
13 
14         RandomListNode head2 = new RandomListNode(head.label);
15         map.put(head,head2);
16         RandomListNode cur = head2;
17 
18         while (head!=null){
19             RandomListNode rand1 = head.random;
20             if (rand1!=null && map.containsKey(rand1)){
21                 cur.random = map.get(rand1);
22             } else if (rand1!=null) {
23                 RandomListNode rand2 = new RandomListNode(rand1.label);
24                 map.put(rand1,rand2);
25                 cur.random = rand2;
26             }
27 
28             if (head.next==null){
29                 cur.next=null;
30             } else {
31                 RandomListNode next = head.next;
32                 if (map.containsKey(next))
33                     cur.next = map.get(next);
34                 else {
35                     RandomListNode next2 = new RandomListNode(next.label);
36                     cur.next = next2;
37                     map.put(next,next2);
38                 }
39             }
40 
41             head = head.next;
42             cur = cur.next;
43         }
44 
45         return head2;        
46     }
47 }