嵌套链表的实现

You guys must have seen nested list (嵌套链表) such as [1, 2, 3, [4, 5, [6, 7]], 8, [9, 0]].

So your task is to improve DouList with nested feature. You can directly copy the codes submitted before and make changes on it. But pay attention to something which had been changed in header file.

NOTICE 1:

front() / back() now returns a DouList for example : a = [1, 2, 3, [4, 5, [6, 7]], 8, [9, 0]] a.front() returns [1] a.back() returns [9, 0]

                   

1. #ifndef SSCPP2014_DOULIST_A_H
2. #define SSCPP2014_DOULIST_A_H
3.  
4. #include<string>
5.  
6. classDouList;
7.  
8. structDouListNode{
9. int elem;
10. DouListNode*prev,*next;
11. DouList*sublist;
12. DouListNode(int e =0,DouListNode*p =0,DouListNode*n =0){
13. elem = e;
14. prev = p;
15. next = n;
16. sublist =0;
17. }
18. };
19.  
20. classDouList{
21. private:
22. DouListNode*_head,*_tail;
23. public:
24. DouList();
25. DouList(constDouList&src);
26. ~DouList();
27. void clear();
28. bool empty()const;
29. std::string to_str()const;
30. DouList front()const;
31. DouList back()const;
32. void push_front(constDouListNode&e);
33. void push_back(constDouListNode&e);
34. void pop_front();
35. void pop_back();
36. voidoperator=(constDouList&other);
37. operatorint();// consider why i define it.
38. friend std::ostream&operator<<(std::ostream &out,
39. constDouList&list);
40. // non-meaning static value
41. };
42.  
43. #endif

           

• #include"DouList.h"
•  
• DouList::DouList(){
• _head = _tail =0;
• }
•  
• DouList::DouList(constDouList&src){
• _head = _tail =0;
• *this= src;
• }
•  
• DouList::~DouList(){
• this->clear();
• }
•  
• voidDouList::clear(){
• DouListNode*t;
• while(_head){
• t = _head;
• if(t->sublist)
• delete t->sublist;
• _head = _head->next;
• delete t;
• }
• _head = _tail =0;
• }
•  
• boolDouList::empty()const{
• return _head ==0?true:false;
• }
•  
• std::string DouList::to_str()const{
• std::string ret ="[";
• if(!this->empty()){
• DouListNode*p = _head->next;
• if(_head->sublist){
• ret += _head->sublist->to_str();
• }else{
• ret += std::to_string((longlongint)(_head->elem));
• }
• while(p){
• if(p->sublist){
• ret +=", "+ p->sublist->to_str();
• }else{
• ret +=", "+ std::to_string((longlongint)(p->elem));
• }
• p = p->next;
• }
• }
• ret +="]";
• return ret;
• }
•  
• DouListDouList::front()const{
• DouList ret;
• if(this->empty())
• return ret;
• if(_head->sublist)
• return*(_head->sublist);
• else
• ret.push_front(*_head);
• return ret;
• }
•  
• DouListDouList::back()const{
• DouList ret;
• if(this->empty())
• return ret;
• if(_tail->sublist)
• return*(_tail->sublist);
• else
• ret.push_back(*_tail);
• return ret;
• }
•  
• voidDouList::push_front(constDouListNode&e){
• if(this->empty()){
• _head = _tail =newDouListNode(e.elem);
• }else{
• _head->prev =newDouListNode(e.elem,0, _head);
• _head = _head->prev;
• if(e.sublist){
• _head->sublist =newDouList(*e.sublist);
• }
• }
• }
•  
• voidDouList::push_back(constDouListNode&e){
• if(this->empty()){
• _head = _tail =newDouListNode(e.elem);
• }else{
• _tail->next =newDouListNode(e.elem, _tail);
• _tail = _tail->next;
• if(e.sublist){
• _tail->sublist =newDouList(*e.sublist);
• }
• }
• }
•  
• voidDouList::pop_front(){
• if(this->empty())
• return;
• if(_head == _tail){
• this->clear();
• return;
• }else{
• _head = _head->next;
• if(_head->prev->sublist)
• delete _head->prev->sublist;
• delete _head->prev;
• _head->prev =0;
• }
• }
•  
• voidDouList::pop_back(){
• if(this->empty())
• return;
• if(_head == _tail){
• this->clear();
• }else{
• _tail = _tail->prev;
• if(_tail->next->sublist)
• delete _tail->next->sublist;
• delete _tail->next;
• _tail->next =0;
• }
• }
•  
• voidDouList::operator=(constDouList&other){
• this->clear();
• _head = _tail =0;
• if(other.empty())
• return;
• _head =newDouListNode(other._head->elem);
• if(other._head->sublist){
• _head->sublist =newDouList(*(other._head->sublist));
• }
• DouListNode*p = _head;
• DouListNode*q = other._head->next;
• while(q){
• p->next =newDouListNode(q->elem, p);
• if(q->sublist){
• p->next->sublist =newDouList(*(q->sublist));
• }
• p = p->next;
• q = q->next;
• }
• _tail = p;
• }
•  
• std::ostream&operator<<(std::ostream &out,constDouList&list){
• out <<list.to_str();
• return out;
• }
•  
• DouList::operatorint(){
• if(_head)
• return _head->elem;
• else
• return0;
• }