// DoubleLinkedList.cpp : 定义控制台应用程序的入口点。 //构造双向链表，实现从控制台输入，插入，删除，求大小size等操作 #include "stdafx.h" #include <iostream> using namespace std; //定义双向链表的节点 template<class T> struct NODE {  NODE<T>* pre;  T data;  NODE<T>* next; }; //定义双向链表容器 template<class T> class DoubleLinkedList { public:  DoubleLinkedList()  {   NODE<T>* q = new NODE<T>;   if (q == NULL)   {    cout << "Fail to malloc the head node." << endl;    return;   }   phead = q;   phead->pre = NULL;   phead->data = NULL;   phead->next = NULL;   T i;   cout << "Please input several integer number, input ctrl+z to the end: " << endl;   while (cin >> i)   {    NODE<T>* p = new NODE<T>;    if (p == NULL)    {     cout << "Fail to malloc a new node." << endl;     return;    }    p->data = i;    q->next = p;    p->pre = q;    p->next = NULL;    q = q->next;   }  }  //容器大小方法  int size()  {   NODE<T>* p = phead->next;   int count(0);   while (p != NULL)   {    count++;    p = p->next;   }   return count;  }  //输出DoubleLinkedLIst中的元素  void print_elements()  {   NODE<T>* p = phead->next;   while (p != NULL)   {    cout << p->data << " ";    p = p->next;   }   cout << endl;  }  //插入一个元素到DoubleLinkedList中，任意合法位置插入  void insert_element(int i, T e)  {    if (i <= this->size())   {    NODE<T>* m = phead;    for (int j = 1; j < i; j ++)    {     m = m->next;    }    NODE<T>* n = m->next;    NODE<T>* p = new NODE<T>;    if (p == NULL)    {     cout << "Failed to malloc the node." << endl;    }    m->next = p;    p->pre = m;    p->data = e;    p->next = n;    n->pre = p;   }   else if (i == (this->size()+1))   {    NODE<T>* m = phead;    for (int j = 1; j < i; j++)    {     m = m->next;    }    NODE<T>* p = new NODE<T>;    if (p == NULL)    {     cout << "Failed to malloc the node." << endl;    }    m->next = p;    p->pre = m;    p->data = e;    p->next = NULL;   }   else   {    cout << "Please input the position number equals or smaller than " << size()+1 << endl;   }  }  //插入一个元素到DoubleLinkedList中，只在末尾插入  void insert_element(T e)  {   NODE<T>* m = phead;   for (int j = 1; j <= size(); j++)   {    m = m->next;   }   NODE<T>* p = new NODE<T>;   if (p == NULL)   {    cout << "Failed to malloc the node." << endl;   }   m->next = p;   p->pre = m;   p->data = e;   p->next = NULL;  }  //删除DoubleLinkedList中的一个元素  void delete_element(int i)  {   NODE<T>* p = phead;   for (int j = 0; j < i; j ++)   {    p = p->next;    if (p == NULL)    {//所要删除的元素超过list的范围     cout << "The size of the list is " << size() << " ,Please input the right number." << endl;     return;    }   }   if(p->next != NULL)   {//删除除最后一个以外的元素    NODE<T>* m = p->pre;    NODE<T>* n = p->next;    m->next = n;    n->pre = m;    delete p;   }   else   {//删除元素为最后一个    NODE<T>* m = p->pre;    m->next = NULL;    delete p;   }  } private:  NODE<T>* phead; }; int _tmain(int argc, _TCHAR* argv[]) {  //测试代码   DoubleLinkedList<int> mylist;  mylist.print_elements();  cout << "The size of the double linked list is : " << mylist.size() << endl;  mylist.insert_element(1, 50);  mylist.print_elements();  mylist.insert_element(6, 80);  mylist.print_elements();  mylist.insert_element(250);  mylist.print_elements();  mylist.delete_element(7);  mylist.print_elements();  return 0; }