C++ class实现双向循环链表(完整代码)

写Delete_all的时候注意一下就好了，先判断空白头结点是不是为NULL

代码如下:

#include <iostream>
using namespace std;
typedef int ElemType;
#define NO 0class Node {friend class LinkList;public:Node(): next(NULL), prior(NULL) {};private:ElemType data;Node *next;Node *prior;
};class LinkList {public:LinkList(): head(NULL) {};~LinkList() {Delete_all();}void Init();void TailCreateList(int n);Node *Locate_i(int i);Node *Locate_e(ElemType e);ElemType Get(int i);bool Insert(ElemType e, int i);bool Delete(int i);void Delete_all();void PrintList();private:Node *head;
};void LinkList::Init() {Delete_all();head = NULL;
}void LinkList::TailCreateList(int n) {Node *p, *s, *r;Delete_all();p = new Node();r = p;for (int i = 1; i <= n; i++) {s = new Node();cin >> s->data;r->next = s;s->prior = r;r = s;}r->next = p;p->prior = r;head = p;
}Node *LinkList::Locate_i(int i) {if (i == 0)return head;Node *p;p = head->next;int j = 1;while ((p != head) && (j < i)) {j++;p = p->next;}if (i == j)return p;else {cout << "position is not correct!!!" << endl;return  NULL;}
}Node *LinkList::Locate_e(ElemType e) {Node *p;p = head->next;while ((p != head) && (p->data != e))p = p->next;if (p != head)return p;else {cout << e << " is not exist!!!" << endl;return NULL;}
}bool LinkList::Insert(ElemType e, int i) {Node *p, *s;p = Locate_i(i - 1);if (p != NULL) {s = new Node();s->data = e;s->next = p->next;p->next->prior = s;p->next = s;s->prior = p;return true;} else {cout << "position is not correct!!!" << endl;return false;}
}bool LinkList::Delete(int i) {Node *p;p = Locate_i(i);if (p != NULL) {p->prior->next = p->next;p->next->prior = p->prior;delete p;return true;} else {cout << "position is not correct!!!" << endl;return false;}
}ElemType LinkList::Get(int i) {Node *p;p = head->next;int j = 1;while ((p != head) && (j < i)) {j++;p = p->next;}if (j == i)return p->data;else {cout << "position is not correct!!!" << endl;return NO;}
}void LinkList::Delete_all() {Node *p, *q;p = head;if (p == NULL) {head = NULL;return;}q = p->prior;q->next = NULL;while (p != NULL) {q = p->next;delete p;p = q;}head = NULL;
}void LinkList::PrintList() {Node *p;p = head->next;while (p != head) {cout << p->data << " ";p = p->next;}cout << endl;
}int main() {LinkList l;l.Init();int n;cin >> n;l.TailCreateList(n);l.PrintList();l.Insert(30, 3);l.PrintList();l.Delete(4);l.PrintList();cout << l.Get(2) << endl;l.PrintList();return 0;
}