Copy List with Random Pointer

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.

思想：先处理线性指针，随后处理随机指针，最后恢复原链表（用HashMap保存）

java代码：

1. public RandomListNode copyRandomList(RandomListNode head) {
2. RandomListNode newhead=null;
3. RandomListNode newtail=null;
4. Map<RandomListNode,RandomListNode> oldListMap = new HashMap<RandomListNode,RandomListNode>();
5. if(head==null) return null;
6. RandomListNode p=head;
7. while(p!=null) {
8. oldListMap.put(p,p.next);
9. RandomListNode p1=p.next;
10. if(newhead==null) {
11. newhead=new RandomListNode(p.label);
12. newtail=newhead;
13. } else {
14. RandomListNode tmp = new RandomListNode(p.label);
15. newtail.next=tmp;
16. newtail=tmp;
17. }
18. newtail.random = p;
19. p.next=newtail;
20. p=p1;
21. }
22. p=newhead;
23. while(p!=null) {
24. RandomListNode tmp = p.random;
25. if(tmp.random==null) p.random=null;
26. else {
27. p.random=tmp.random.next;
28. }
29. p=p.next;
30. }
31. p=head;
32. while(oldListMap.get(p)!=null) {
33. p.next=oldListMap.get(p);
34. p=p.next;
35. }
36. p.next=null;
37. return newhead;
38. }

C++代码：

1. RandomListNode *copyRandomList(RandomListNode *head) {
2. if(!head) return head;
3. RandomListNode *p=head;
4. RandomListNode *new_head=NULL;
5. RandomListNode *tail=NULL;
6. std::map<RandomListNode *,RandomListNode *> oldlistMap;
7. while(p!=NULL) {
8. RandomListNode *tmp=p;
9. if(new_head==NULL) {
10. new_head=new RandomListNode(p->label);
11. tail=new_head;
12. } else {
13. RandomListNode *new_tmp = new RandomListNode(tmp->label);
14. tail->next=new_tmp;
15. tail=new_tmp;
16. }
17. oldlistMap[p]=p->next;
18. p = p->next;
19. tail->random=tmp;
20. tmp->next=tail;
21. }
22. p=new_head;
23. while(p!=NULL) {
24. RandomListNode *tmp=p;
25. RandomListNode *cur=p;
26. RandomListNode *tmp_k = tmp->random;
27. if(tmp_k!=NULL)
28. cur->random=tmp_k->next;
29. else cur->random=NULL;
30. p=p->next;
31. }
32. p=head;
33. while(p!=NULL) {
34. RandomListNode *tmp=oldlistMap[p];
35. p->next=tmp;
36. p=tmp;
37. }
38. return new_head;
39. }