（链表）18-随机链表的复制

 1 /*
 2 class Node {
 3     int val;
 4     Node next;
 5     Node random;
 6 
 7     public Node(int val) {
 8         this.val = val;
 9         this.next = null;
10         this.random = null;
11     }
12 }
13 */
14 
15 class Solution {
16     public Node copyRandomList(Node head) {
17         // 判空入参
18         if(head == null){
19             return null;
20         }
21         // 申请临时指针
22         Node cur = head;
23         // 申请HashMap用于存储复制节点
24         HashMap<Node,Node> map = new HashMap<>();
25         // 拷贝复制节点到HashMap
26         while(cur != null){
27             map.put(cur,new Node(cur.val));
28             cur = cur.next;
29         }
30         // 针对新节点的next指针和random指针进行赋值
31         cur=head;
32         while(cur!=null){
33             map.get(cur).next=map.get(cur.next);
34             map.get(cur).random=map.get(cur.random);
35             cur=cur.next;
36         }
37         // 返回结果
38         return map.get(head);
39     }
40 }