leetcode

0 class Solution {

1 public:

2 Node *copyRandomList(Node *head) {

3 if (!head) return nullptr;

4

5 unordered_map<Node *, Node *> um;

6 Node *h, *t;

7 t = h = new Node(-1);

8 for (Node *p = head; p; p = p->next) {

9 t = t->next = new Node(p->val);

10 um.insert(make_pair(p, t));

11 }

12

13 t = h->next;

14 for (Node *p = head; p; p = p->next, t = t->next) {

15 if (p->random != nullptr) t->random = um[p->random];

16 }

17 return h->next;

18 }

19 };