C++实现双链表

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C++实现双链表
#include<iostream>#include<assert.h>using namespace std;typedef int DataType;struct ListNode{    DataType _data;    ListNode *_next;    ListNode *_prev;    ListNode(const DataType x)        :_data(x), _next(NULL), _prev(NULL)    {}};class List{    typedef ListNode Node;public:    List()        :_head(NULL), _tail(NULL)    {    }    void PushBack(DataType x)    {        if (_head == NULL)        {            _head = _tail = new Node(x);        }        else        {            Node* tmp = new Node(x);            _tail->_next = tmp;             tmp->_prev = _tail;            _tail = _tail->_next;        }    }    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 = tmp;        }    }    void Display()    {        if (_head == NULL)            return;        else        {            Node* cur(_head);            while (cur != NULL)            {                cout << cur->_data << " ";                cur = cur->_next;            }            cout << endl;        }    }    void PopBack()    {        if (_head == NULL||_head==_tail)        {            delete _tail;            _head = _tail = NULL;        }        else        {            _tail = _tail->_prev;            delete _tail->_next;        }    }    void PopFront()    {        if (_head == NULL || _head == _tail)        {            delete _tail;            _head = _tail = NULL;        }        else        {            _head = _head->_next;            delete _head->_prev;        }    }    void Destroy()    {        if (_head == _tail)        {            delete _tail;            _head = _tail = NULL;        }        else        {            while (_head->_next != NULL)            {                _head = _head->_next;                delete _head->_prev;            }            delete _tail;            _head = _tail = NULL;        }    }    Node* Find(DataType x)    {        if (_head == NULL)            return NULL;        else        {            Node *cur(_head);            while (cur != NULL)            {                if (cur->_data == x)                {                    break;                }                cur = cur->_next;            }            return cur;        }    }    void Insert(Node* pos, DataType x)    {        assert(pos);        if (pos == _head)        {            PushFront(x);        }        else        {            Node *tmp = new Node(x);            tmp->_next = pos;            pos->_prev->_next = tmp;            tmp->_prev = pos->_prev;            pos->_prev = tmp;        }    }    void Erase(Node* pos)    {        assert(pos);        if (pos == _head)        {            _head = _head->_next;            delete pos;        }        else        {            pos->_next->_prev = pos->_prev;            pos->_prev->_next = pos->_next;            delete pos;            pos = NULL;        }    }    void Reverse()//定义了一个NewHead 让其从第一个一直走到最后一个，将其再给_head    {        if (_head == _tail)        {            return;        }        else        {            ListNode* cur = _head;            ListNode* tmp = cur;            ListNode* NewHead = NULL;            while (cur)            {                tmp = cur;                cur = cur->_next;                tmp->_next = NewHead;                tmp->_prev = cur;                NewHead = tmp;            }            _head = NewHead;            }    }private:    Node *_head;    Node *_tail;};void test(){    List l1;    l1.PushBack(0);    l1.PushBack(1);    l1.PushBack(2);    l1.PushBack(3);    /*l1.PushFront(2);    l1.PushFront(1);    l1.PushFront(0);*/    /*l1.PopBack();    l1.PopBack();    l1.PopBack();*/    //l1.PopFront();    //l1.PopFront();    //l1.PopFront();    //l1.Destroy();    //l1.Find(1);    //l1.Insert(l1.Find(5), 9);    //l1.Insert(l1.Find(1), 6);    //l1.Insert(l1.Find(3), 5);    //l1.Insert(l1.Find(0), 9);    //l1.Erase(l1.Find(1));    //l1.Erase(l1.Find(10));    l1.Reverse();    l1.Display();}int main(){    test();    system("pause");    return 0;}
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