数据结构--循环双向链表

struct DuListNode{
int val;
DuListNode *prev,*next;
DuListNode(int x):val(x),prev(NULL),next(NULL){}
};

#include<iostream>
#include<cstdlib>
#include<assert.h>

using namespace std;

struct DuListNode{
int val;
DuListNode *prev,*next;
DuListNode(int x):val(x),prev(NULL),next(NULL){}
};

typedef DuListNode * DuListHead;

class DuList{
private:
//DuListNode *prev;
//DuListNode *next;
int val;
DuListHead head;<span style="white-space:pre">	</span>// 该链表只需要头节点即可。
public:
DuList();
~DuList();

//void Init();
bool IsEmpty();
void Clear();
int Length();
DuListNode *GetElem(int);
void Insert(int, int);
void Delete(int);
void Traverse();
void RevTraverse();
};
DuList::DuList()
{
cout << "Construst..." << endl;
head = new DuListNode(0);
head->prev = head;
head->next = head;
}

DuList::~DuList()
{
if(head == NULL)return;
DuListNode* q, *p = head->next;
while(p != head)
{
q = p->next;
delete p;
p = q;
}
free(head); //head node
head = NULL;
}

bool DuList::IsEmpty()
{
if(head->next == head && head->prev== head)
return true;
else
return false;
}

void DuList::Clear()
{
DuListNode *q, *p = head->next;
while(p != head)
{
q = p->next;
delete p;
p = q;
}
head->next = head;
head->prev = head;
}

int DuList::Length()
{
int i = 0;
DuListNode *p = head->next;
while(p != head)
{
i++;
p = p->next;
}
return i;
}
DuListNode * DuList::GetElem(int i)//返回第i个链表节点
{
int j = 1;
DuListNode *p = head->next;
while( p != head && j < i)
{
j++;
p = p->next;
}
if (p == head || j < i)
return NULL;
else
return p;
}

void DuList::Insert(int i, int x)//在链表的第i个位置插入值为x的节点
{
if(i<0)
return;
cout << "Insert..." << i << x << endl;
DuListNode *node = new DuListNode(x);
DuListNode *curPrev;
if(i == 0)
curPrev = head;
else
curPrev = GetElem(i-1);
DuListNode *tNext = curPrev->next;
node->next = tNext;
tNext->prev = node;
node->prev = curPrev;
curPrev->next = node;
return;
}
//delete node which number is value
void DuList::Delete(int x)//删除第一个值为x的节点
{
DuListNode *q = head ,*p = head->next;
while(p != head && p->val != x)
{
q = p;
p = p->next;
}
if(p == head)
cout << "elem not exist.." << endl;
else
{
assert(p->val == x);
assert(q->next == p);
q->next = p->next;
p->next->prev = q;
delete p;
p = NULL;
}
return;
}

void DuList::Traverse()//遍历链表中的节点
{
DuListNode *q, *p = head->next;
while(p != head)
{
cout << p->val << " ";
p = p ->next;
}
cout << endl;
}

void DuList::RevTraverse()//反序遍历链表中的节点
{
DuListNode *p = head->prev;
while( p != head)
{
cout << p->val <<  " ";
p = p->prev;
}
cout << endl;
}
int main()
{

DuList L1;
if(L1.IsEmpty())
cout << "L1 is empty..." << endl;
L1.Insert(0,5);
L1.Insert(0,3);
L1.Insert(0,2);
L1.Insert(0,1);
L1.Insert(4,4);
L1.Traverse();
L1.RevTraverse();
DuListNode *node(NULL);
if(node = L1.GetElem(2))
cout << node->val << endl;
L1.Delete(2);
L1.Traverse();
L1.RevTraverse();

return	EXIT_SUCCESS;
}