给定一个链表，每个节点包含一个额外增加的随机指针，该指针可以指向链表中的任何节点或空节点。
要求返回这个链表的深度拷贝。
代码
class Solution {
public:
RandomListNode *copyRandomList(RandomListNode *head) {
if (!head) return NULL;
RandomListNode *res = new RandomListNode(head->label);
RandomListNode *node = res;
RandomListNode *cur = head->next;
map<RandomListNode*, RandomListNode*> m;
m[head] = res;
while (cur) {
RandomListNode *tmp = new RandomListNode(cur->label);
node->next = tmp;
m[cur] = tmp;
node = node->next;
cur = cur->next;
}
node = res;
cur = head;
while (node) {
node->random = m[cur->random];
node = node->next;
cur = cur->next;
}
return res;
}
};
