C++实现双向链表

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上一篇用C++实现了单链表。今天呢，我们来看看双向链表如何通过C++实现。双向链表也叫双链表，它的的每个数据节点都有两个指针，分别指向直接后继和直接前驱。所以从双向链表中的任何一个节点开始，都可以很方便的访问它的前驱节点和后继节点。

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#include<iostream>#include<assert.h>using namespace std;typedef int DataType;struct DListNode   //节点的创建{    DataType data;    DListNode* next;    DListNode* prev;    DListNode(DataType x)  //节点初始化        :data(x),next(NULL),prev(NULL)    {}};class DList{    typedef DListNode Node;public:    DList()        :_head(NULL), _tail(NULL)    {}    DList(const DList& l)        :_head(NULL),_tail(NULL)    {        if (l._head == NULL)        {            return;        }        else        {            Node* cur = l._head;            while (cur)            {                PushBack(cur->data);                cur = cur->next;            }        }    }    //DList& operator=(const DList& l)    //传统写法    //{    //  if (this != &l)    //  {    //      _head = NULL;    //      _tail = NULL;    //      Node* cur = l._head;    //      while (cur)    //      {    //          PushBack(cur->data);    //          cur = cur->next;    //      }    //      _tail->next = NULL;    //  }    //  return *this;    //}    //DList& operator=(const DList& l)  //现代写法    //{    //  if (this != &l)    //  {    //      DList tmp(l);    //      swap(_head, tmp._head);    //      swap(_tail, tmp._tail);    //  }    //  return *this;    //}    DList& operator=(const DList l)    // 再优化，传值操作    {        if (this != &l)        {            DList tmp(l);            swap(_head, tmp._head);            swap(_tail, tmp._tail);        }        return *this;    }    ~DList()    {        Clear();    }    void PushBack(DataType x)    {        if (_head == NULL)        {            _head = new Node(x);            _tail = _head;        }        else        {            Node* tmp = new Node(x);            _tail->next = tmp;            tmp->prev = _tail;            _tail = _tail->next;        }        return;    }    void PopBack()    {        if (_head == NULL)        {            return;        }        else if (_head == _tail)        {            delete _tail;            _head = NULL;            _tail = NULL;            return;        }        else        {            Node* per = _tail;            _tail = _tail->prev;            delete per;            _tail->next = NULL;            return;        }    }    void PushPront(DataType x)    {        if (_head == NULL)        {            _head = new Node(x);            _tail = _head;        }        else        {            Node* tmp = new Node(x);            tmp->next = _head;            _head->prev = tmp;            _head = _head->prev;        }        return;    }    void PopPront()    {        if (_head == NULL)        {            return;        }        else if (_head == _tail)        {            delete _tail;            _tail = NULL;            _head = NULL;            return;        }        else        {            Node* cur = _head;            _head = _head->next;            delete cur;            _head->prev = NULL;        }    }    void Insert(Node* pos,DataType x)    {        assert(pos);        if (pos == _head)        {            PushPront(x);        }        else if (pos == _tail)        {            PushBack(x);        }        else        {            Node* tmp = new Node(x);            Node* head = pos->prev;            head->next = tmp;            tmp->prev = head;            tmp->next = pos;            pos->prev = tmp;        }        return;    }    Node* Find(DataType x)    {        Node* cur = _head;        while (cur->data != x)        {            cur = cur->next;        }        return cur;    }    void Erase(Node* pos)    {        assert(pos);        if (pos == _head)        {            PopPront();        }        else if (pos == _tail)        {            PopBack();        }        else        {            Node* cur = _head;            while (cur != pos)            {                cur = cur->next;            }            pos->prev->next = pos->next;            pos->next->prev = pos->prev;            delete pos;        }    }    //void Reverse()     //对称位置值交换    //{    //  Node* cur1 = _head;    //  Node* cur2 = _tail;    //  while ((cur1 != cur2)&&(cur1->prev != cur2))    //  {    //      swap(cur1->data, cur2->data);    //      cur1 = cur1->next;    //      cur2 = cur2->prev;    //  }    //  return;    //}    void Reverse()      //通过交换每一个节点上的两个指针来实现逆置    {        Node* cur = _head;        while (cur)        {            Node* next = cur->next;            swap(cur->next, cur->prev);            //cur = cur->prev;            cur = next;        }        swap(_head, _tail);    }    void Clear()    {        while (_head)        {            Node* cur = _head;            _head = _head->next;            delete cur;        }        _head = _tail = NULL;    }    void Display()    {        Node* cur = _head;        while (cur)        {            cout << cur->data << "-";            cur = cur->next;        }        cout << endl;    }private:    Node* _head;    Node* _tail;};void Test1(){    DList l1;    l1.PushBack(1);    l1.PushBack(2);    l1.PushBack(3);    l1.PushBack(4);    l1.Display();    DList l2(l1);    l2.Display();    l1.PopBack();    l1.PopBack();    l1.PopBack();    l1.PopBack();    l1.Display();}void Test2(){    DList l1;    l1.PushPront(1);    l1.PushPront(2);    l1.PushPront(3);    l1.PushPront(4);    l1.Display();    l1.PopPront();    l1.PopPront();    l1.PopPront();    l1.PopPront();    l1.Display();}void Test3(){    DList l1;    l1.PushBack(1);    l1.PushBack(2);    l1.PushBack(3);    l1.PushBack(4);    l1.Insert(l1.Find(3), 9);    l1.Display();    l1.Erase(l1.Find(3));    l1.Display();    l1.Reverse();    l1.Display();    DList l2;    l2 = l1;    l2.Display();}int main(){    Test3();    system("pause");    return 0;}

上一篇我们已经详细讲解了单链表的实现，双向链表与之差不了多少，只是每个节点上多了一个指向直接前驱的指针，所以，这里就不进行详细讲解。多见谅！！！

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