双向链表的初始化，建立，添加节点和删除节点（注意插入和删除要分三种情况）

/*双向循环链表*/
#include "declaration.h"
typedef struct DulNode
{
int data;
struct DulNode *next,*prior;
}DulNode,*DulLinkList;

Status InitList_DUL(DulLinkList &L)//初始化一个带头结点的双向循环链表,ok
{
L=(DulNode*)malloc(sizeof(DulNode));
L->next=L;
L->prior=L;
if (!L)
exit(OVERFLOW);
return OK;
}

void DestoryList_DUL(DulLinkList &L)//销毁一个带头结点的双向循环链表,ok
{
DulNode *p;
while(L)
{
p=L->next;
free( L);
L=p;
}
}

void CreateList_DUL(DulLinkList &L)//正序创建一个带头结点的双向循环链表,ok
{
DulLinkList p,s;//中间变量
int n,i;
printf("input Length: \n");
scanf("%d",&n);
p=L;
printf("input value with enter:");
for(i=n;i>0;i--)
{
s=(DulLinkList)malloc(sizeof(DulNode));
scanf("%d",&s->data);
p->next=s;
s->prior=p;
p=s;
}
p->next=L;
L->prior=p;
}

DulLinkList LocateELem_DUL(DulLinkList L,ElemType x)
{//定位值为e的结点的位置
DulNode *p;
p=L->next;
while(p!=L)
{
if(!compare(x,p->data))
return p;
p=p->next;
}
printf("the element is not exists\n");
return NULL;
}

Status InsertAfter_DUL(DulLinkList &L,ElemType y)//在带头结点的双向循环链表中的x值后插入y值,李大友2.15
{
DulLinkList p,s;
ElemType x;
printf("value you want to find is :");
scanf("%d",&x);
p=LocateELem_DUL(L,x);
if(!p)
{
printf("%d not exists.\n",x);
return ERROR;
}
s=(DulLinkList)malloc(sizeof(DulNode));
s->data=y;
s->next=p->next;
p->next->prior=s;
p->next=s;
s->prior=p;
return OK;
}//LinkList_L

//删除

DulNode* deleteTheNode(DulNode* head,int num)
{
DulNode* p1,*p2;
p1=head;
while (p1->next&&num!=p1->data)
{
p1=p1->next;
}
if (num==p1->data)
{
if (p1==head)//找到的是头节点
{
head=head->next;
head->prior=NULL;
}
else if(p1->next)//不是头结点,也不是尾节点
{
p1->next->prior=p1->prior;
p1->prior->next=p1->next;
}
else
{
p1->prior->next=NULL;

free(p1);
}
}
else
{
//cout<<"节点未找到"<<endl;
printf("节点未找到");
}
return head;
}

//主函数如下
void main()
{
DulLinkList p;
DulLinkList L;
InitList_DUL(L);
//	NCreateList_L(L);//逆位序建立链表
CreateList_DUL(L);//正序建立双向循环链表
ListTraverse_DUL(L);
//	ListPrint_L(L);
//	Reverse_DulLinkList(L);//OK
//	ListTraverse_DUL(L);
//	ListPrint_DUL(L);
ElemType y;
printf("the insert value is :");
scanf("%d",&y);
//	InsertBefore_DUL(L,y);//OK
InsertAfter_DUL(L,y);  //OK
ListTraverse_DUL(L);
//	ListPrint_DUL(L);

ElemType z;
printf("the delete value is :");
scanf("%d",&z);
deleteTheNode(L,z);
ListTraverse_DUL(L);

}