C++模拟双向链表的基本操作

双向链表也叫双链表，是链表的一种，它的每个数据结点中都有两个指针，分别指向直接后继和直接前驱。所以，从双向链表中的任意一个结点开始，都可以很方便地访问它的前驱结点和后继结点。一般我们都构造双向循环链表。

双（向）链表中有两条方向不同的链，即每个结点中除next域存放后继结点地址外，还增加一个指向其直接前趋的指针域pre。双向链表在查找时更方便 特别是大量数据的遍历

注意：
    　①双链表由头指针head惟一确定的。
    　②带头结点的双链表的某些运算变得方便。
    　③将头结点和尾结点链接起来，为双（向）循环链表。

双链表的基本操作：

<pre name="code" class="cpp">#include <iostream>using namespace std;#include <assert.h>#define DataType intstruct Node{//Node(const DataType& data = 0);Node* _pNext;Node* _pPre;DataType _data;};class List{public:List():_size(0),_pHead(NULL),_pTail(NULL){}List(DataType arr[], size_t size):_pHead(NULL),_pTail(NULL),_size(0){size_t i = 0;for(i=0; i<_size; i++){PushBack(arr[i]);}}List(const List& l):_size(0),_pHead(NULL),_pTail(NULL){Node* temp = _pHead;_pHead->_pPre = NULL;Node* CurNode = l._pHead;while(CurNode){temp = CurNode;CurNode = CurNode->_pNext;temp = temp->_pNext;_size++;}temp->_pNext = NULL;}List& operator=(const List& l){if(this != &l){Node* temp = _pHead;_pHead->_pPre = NULL;Node* CurNode = l._pHead;while(CurNode){temp = CurNode;CurNode = CurNode->_pNext;temp = temp->_pNext;_size++;}temp->_pNext = NULL;    }}~List(){if(NULL != this){Clear();}}void PushBack(const DataType& data);void PopBack();void PushFront(const DataType& data);void PopFront();bool Empty()const;Node* Find(const DataType& data)const;void Insert(Node* pos, const DataType& data);void Erase(Node* pos);void Remove(const DataType& data);size_t Size()const;void Clear();Node& Front();const Node& Front()const;Node& Back();Node& Back()const;private:Node* BuyNode(const DataType &data){Node *NewNode = new Node;NewNode->_data = data;return NewNode;}friend ostream& operator<<(ostream& _cout, const List& l){Node* pCur = l._pHead;while(pCur){_cout<<pCur->_data<<"<-->";pCur = pCur->_pNext;}_cout<<"end";return _cout;}private:size_t _size;Node* _pHead;Node* _pTail;};void List::PushBack(const DataType& data){if(_size == 0)//链表为空{_pHead = _pTail = BuyNode(data);_pHead->_pPre = NULL;_pTail->_pNext = NULL;}else//链表不为空{Node* temp = BuyNode(data);Node* CurNode = _pHead;while(CurNode->_pNext){CurNode = CurNode->_pNext;}temp->_pPre = CurNode;CurNode->_pNext = temp;temp->_pNext = NULL;_pTail = temp;}_size++;}void List::PopBack(){if(_size == 0)//链表为空{assert(false);return;}else if(_size == 1)//链表仅有一个节点{Node* pDel = _pTail;delete pDel;_pHead = _pTail = NULL;_size--;}else//有多个节点{Node* pDel = _pTail;_pTail = _pTail->_pPre;        _pTail->_pNext = NULL;delete pDel;_size--;}}void List::PushFront(const DataType& data){if(_size == 0)//链表为空{_pHead = BuyNode(data);_pTail = _pHead;_pHead->_pPre = NULL;_pTail->_pNext = NULL;}else//链表不为空{Node* temp = BuyNode(data);temp->_pNext = _pHead;_pHead->_pPre = temp;_pHead = temp; }_size++;}void List::PopFront(){if(_size == 0){assert(false);return;}else if(_size == 1){Node* pDel = _pHead;delete pDel;_pHead = _pTail = NULL;_size--;}else{Node* pDel = _pHead;_pHead = _pHead->_pNext;_pHead->_pPre = NULL;delete pDel;_size--;}}bool List::Empty()const{return _size==0;}Node* List::Find(const DataType& data)const{Node* pCur = _pHead;while(pCur){if(pCur->_data == data)return pCur;elsepCur = pCur->_pNext;}return pCur;}void List::Insert(Node* pos, const DataType& data)//插入到pos之前{if(pos == _pHead){PushFront(data);}else{Node* pCur = _pHead;while(pCur->_pNext != pos){pCur = pCur->_pNext;}Node* temp = BuyNode(data);pCur->_pNext = temp;pos->_pPre = temp;temp->_pPre = pCur;temp->_pNext = pos;}_size++;}//void List::Insert(Node* pos, const DataType& data)//插入到pos之后//{//if(pos == _pTail)//{//PushBack(data);//}//else//{//Node* pCur = _pHead;//while(pCur != pos->_pNext)//{//pCur = pCur->_pNext;//}//Node* temp = BuyNode(data);//pCur->_pPre = temp;//pos->_pNext = temp;//temp->_pPre = pos;//temp->_pNext = pCur;//}//_size++;//}void List::Erase(Node* pos){if(pos == _pHead){PopFront();}else if(pos == _pTail){PopBack();}else{Node* pDel = _pHead; Node* pPre = _pHead;while(pDel != pos){pPre = pDel;pDel = pDel->_pNext;}pPre->_pNext = pDel->_pNext;pos->_pNext->_pPre = pPre;delete pDel;}_size--;}void List::Remove(const DataType& data)//删除第一个值为data的数据{Erase(Find(data));}size_t List::Size()const{return _size;}void List::Clear(){if(_size == 0){return;}else{Node* pDel = _pHead;Node* pCur = _pHead->_pNext;while(pCur->_pNext){pCur = pCur->_pNext;pDel = pCur->_pPre;delete pDel;}delete pCur;_pTail = NULL;pDel = _pHead;delete pDel;_pHead = NULL;_size = 0;}}Node& List::Front(){assert(Empty());return *_pHead;}const Node& List::Front()const{assert(Empty());return *_pHead;}Node& List::Back(){assert(Empty());return *_pTail;}Node& List::Back()const{assert(Empty());return *_pTail;}int main(){List l1;l1.PushBack(1);l1.PushBack(2);l1.PushBack(3);cout<<l1<<endl;l1.PopBack();cout<<l1<<endl;l1.PopBack();cout<<l1<<endl;l1.PopBack();cout<<l1<<endl;l1.PopBack();cout<<l1<<endl;List l1;l1.PushFront(5);cout<<l1<<endl;l1.PushBack(1);l1.PushBack(2);l1.PushBack(3);cout<<l1<<endl;l1.PushFront(4);cout<<l1<<endl;Node* ret = l1.Find(4);ret = l1.Find(2);l1.Erase(ret);cout<<l1<<endl;l1.Insert(ret,6);cout<<l1<<endl;ret = l1.Find(3);ret = l1.Find(6);l1.PopFront();cout<<l1<<endl;l1.PopFront();l1.PopFront();l1.PopFront();cout<<l1<<endl;l1.PopFront();l1.Clear();cout<<l1<<endl;List l1;l1.PushBack(1);l1.PushBack(2);l1.PushBack(1);l1.PushBack(1);    l1.Remove(1);cout<<l1<<endl;system("pause");return 0;}