copy a random link

题目：

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.

 1 /**
 2 * Definition for singly-linked list with a random pointer.
 3 * struct RandomListNode {
 4 *     int label;
 5 *     RandomListNode *next, *random;
 6 *     RandomListNode(int x) : label(x), next(NULL), random(NULL) {}
 7 * };
 8 */
 9 class Solution {
10 public:
11     RandomListNode *copyRandomList(RandomListNode *head) {
12         if(head == NULL) return NULL;
13         //将新节点复制到原来节点后面
14         RandomListNode *copy;
15         RandomListNode *p = head;
16         RandomListNode *tmp;
17         while(p!=NULL)
18         {
19             copy = new RandomListNode(p->label);
20             tmp = p->next;
21             p->next = copy;
22             copy->next = tmp;
23             p = tmp;
24         }
25         //将新结点与随机结点相连接     
26         p = head;
27         copy = head->next;
28         while(p!=NULL && copy!=NULL)
29         {
30             copy->random = ((p->random)?p->random->next:NULL);
31             p = ((copy->next)?copy->next:NULL);
32             copy = ((p->next)?p->next:NULL);
33         }
34         //将新节点与原结点拆开
35         p = head;
36         head = copy = head->next;
37         while(p!=NULL && copy!=NULL)
38         {
39             p->next = ((copy->next)?copy->next:NULL);
40             p = ((p->next)?p->next:NULL);
41             copy->next = ((p)?p->next:NULL);
42             copy = ((copy->next)?copy->next:NULL);
43         }
44         return head;
45     }
46 };