C++实现双链表基本接口

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首先先简单通过图示区分单链表和双链表的结构差异：

这里写图片描述

单链表的基本接口实现可参考：单链表简单实现

接下来就是双链表的基本接口实现：

#include <iostream>#include <assert.h>using namespace std;typedef int DataType;struct ListNode{    ListNode* _next;    ListNode* _prev;    DataType _data;    ListNode(DataType x)        :_next(NULL)        , _prev(NULL)        , _data(x)    {}};typedef ListNode Node;class List{public:    List()        :_head(NULL)        ,_tail(NULL)    {}    List(const List& l)        :_head(NULL)        ,_tail(NULL)    {        Copy(l);    }    void Copy(const List& l)    {        Node* cur = l._head;        while (cur)        {            PushBack(cur->_data);            cur = cur->_next;        }    }    List& operator=(const List& l)    {        Destory();        Copy(l);        return *this;    }    ~List()    {        Destory();    }    void Destory()    {        if (_head)        {            Node* cur = _head;            while (_head)            {                cur = _head;                _head = _head->_next;                delete cur;            }            _head = _tail = NULL;        }    }    void PushBack(DataType x)    {        if (_head == NULL)        {            Node* tmp = new Node(x);            tmp->_next = tmp->_prev = NULL;            _head = _tail = tmp;        }        else        {            Node* tmp = new Node(x);            _tail->_next = tmp;            tmp->_prev = _tail;            _tail = tmp;        }    }    void PopBack()    {        if (_head == NULL)        {            return;        }        else if (_head->_next == NULL)        {            delete _head;            _head = _tail = NULL;        }        else        {            Node* tmp = _tail;            _tail = _tail->_prev;            _tail->_next = NULL;            delete tmp;        }    }    void PushFront(DataType x)    {        if (_head == NULL)        {            _head = _tail = new Node(x);        }        else        {            Node* tmp = new Node(x);            tmp->_next = _head;            _head->_prev = tmp;            _head = _head->_prev;        }    }    void PopFront()    {        if (_head == NULL)        {            return;        }        else if (_head->_next == NULL)        {            delete _head;            _head = _tail = NULL;        }        else        {            Node* tmp = _head;            _head = _head->_next;            delete tmp;            _head->_prev = NULL;        }    }    Node* Find(DataType x)    {        Node* cur = _head;        while (cur)        {            if (cur->_data == x)                return cur;            cur = cur->_next;        }        return NULL;    }    // 在pos的前面插入x    void Insert(Node* pos, DataType x)    {        assert(pos);        if ((pos == 0) || (pos->_prev == NULL))        {            PushFront(x);        }        else        {            Node* font = pos->_prev;            Node* tmp = new Node(x);            tmp->_prev = font;            tmp->_next = pos;            font->_next = tmp;            pos->_prev = tmp;        }    }    //删除pos位置的元素    void Erase(Node* pos)    {        assert(pos);        if ((pos == 0) || (pos->_prev == NULL))        {            PopFront();        }        else if (pos->_next == NULL)        {            PopBack();        }        else        {            Node* font = pos->_prev;            Node* last = pos->_next;            font->_next = last;            last->_prev = font;            delete pos;        }    }    //逆序整个双链表    void Reverse()    {        Node* cur = _head;        while (cur)        {            swap(cur->_next,cur->_prev);            cur = cur->_prev;        }        swap(_head, _tail);    }    void Print()    {        Node* cur = _head;        while (cur)        {            cout << cur->_data << "->";            cur = cur->_next;        }        cout << "NULL" << endl;    }private:    Node* _head;    Node* _tail;};

注：在一些操作实现时，一定要要考虑清楚各种情况，再进行情况的分类尽量提高代码的复用程度。

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