双向循环链表的创建，插入和遍历

双向循环链表的创建，插入和遍历

//  test13.cpp : Defines the entry point for the console application.
//
#include  " stdafx.h "
#include < iostream >
using   namespace  std;

#define  ElemType int

typedef  struct  DuLNode{
    ElemType data;
    DuLNode *  next;
    DuLNode *  prior;
}DuLNode,  * DuLinkList;

/* *
ListInsert(L, pos, d)
    p=L[pos-1]
    node->next=p->next
    p->next=node    
    node->prior=p;
    node->next->prior=node
*/
int  ListInsert(DuLinkList &  L,  int  pos, ElemType d){
    DuLNode *  p = L;   // p用于遍历List
     if (pos <= 0 )  return   - 1 ;  // 只能在头结点（pos=0）之后插入
     for ( int  i = 0 ;i < pos - 1 ;i ++ )  // 寻找插入位置的前一个结点
        p = p -> next;
    DuLNode *  node = (DuLNode * )malloc( sizeof (DuLNode));
    node -> data = d;
    node -> next = p -> next;
    p -> next = node;
    node -> prior = p;
    node -> next -> prior = node;
     return   1 ;
}

ostream &   operator << (ostream &   out , DuLinkList &  L){  // 重载<<便于输出DuLinkList
    DuLNode *  p = L -> next；  // 如果要往前遍历，就p=L->prior
     while (p  &&  p != L){
         out << p -> data << " <--> " ;
        p = p -> next;    // 如果要往前遍历，就p=p->prior
    }
     out << " NULL " ;
     return   out ;
}


int  main(){
    DuLinkList list = (DuLNode * )malloc( sizeof (DuLNode));
    list -> data =- 1 ;  // head结点，默认为-1
    list -> next = list;
    list -> prior = list;
     for ( int  i = 0 ;i < 10 ;i ++ ){
        ListInsert(list,i + 1 , i * i);
    }
    cout << list;
    system( " pause " );
}