双向循环链表程序

//dblist.h

#include <stdio.h>
#include <stdlib.h>

typedef struct tagDbNode
{
 int data;
 struct tagDbNode * left;
 struct tagDbNode * right;
} DbNode, * pdbNode;


//创建结点
pdbNode CreateNode(int data)
{
 pdbNode pnode = (pdbNode)malloc(sizeof(DbNode));
 pnode->data = data;
 pnode->left = pnode->right = pnode; //创建新结点时，让其前驱和后继指针都指向自身
 
 return pnode;
}

//创建链表
pdbNode CreateList(int head)  //参数给出表头结点数据 （表头结点不作为存放有意义数据的结点）
{
 pdbNode pnode = (pdbNode)malloc(sizeof(DbNode));
 pnode->data = head;
 pnode->left = pnode->right = pnode; 
 return pnode;
}

//插入新结点,总是在表尾插入; 返回表头结点
pdbNode InsertNode(pdbNode node, int data) // 参数1是链表的表头结点，参数2是要插入的结点（结

点数据为data）
{
 pdbNode pnode = CreateNode(data);
 
 // 从左到右恢复链接
 node->left->right = pnode;
 pnode->right = node;
 
 // 从右到左恢复链接
 pnode->left = node->left;
 node->left = pnode;
  
 return node;
}

//查找结点，成功则返回满足条件的结点指针，否则返回NULL
pdbNode FindNode(pdbNode node, int data) // 参数1是链表的表头结点，参数2是要查找的结点（其中

结点数据为data）
{
 pdbNode pnode = node->right;
 while (pnode != node && pnode->data != data)
 {
  pnode = pnode->right;
 } 
 if (pnode == node)  return NULL; 
 return pnode;
}

//删除满足指定条件的结点, 返回表头结点, 删除失败返回NULL（失败的原因是不存在该结点）
pdbNode DeleteNode(pdbNode node, int data) // 参数1是链表的表头结点，参数2是要删除的结点（其

中结点数据为data）
{
 pdbNode pnode = FindNode(node, data); 
 if (NULL == pnode) return NULL; 
 pnode->left->right=pnode->right;
 pnode->right->left=pnode->left;
 free(pnode); 
 return node;
}

//获取链表的长度
int GetLength(pdbNode node) // 参数为链表的表头结点
{
 int nCount = 0; 
 pdbNode pnode = node->right; 
 while (pnode!= node)
 {
     pnode = pnode->right;  
  nCount++;
 } 
 return nCount;
}

//顺序打印整个链表
void PrintList(pdbNode node) // 参数为链表的表头结点
{
 pdbNode pnode;
 if (NULL == node) return;
 pnode= node->right;
 while (pnode != node)
 {
  printf("%d   ", pnode->data);
  pnode = pnode ->right;
 } 
 printf("\n");
}

//将链表反序打印
void ReverPrint(pdbNode node) //参数为链表的表头结点
{
 pdbNode pnode;
 if (NULL == node) return; 
 pnode= node->left;
 while (pnode != node)
 {
  printf("%d   ", pnode->data);
  pnode = pnode->left;
 } 
 printf("\n");
}

//删除链表
void DeleteList(pdbNode node) //参数为链表表头结点
{
 pdbNode pnode = node->right;
 pdbNode ptmp;
 if (NULL == node) return; 
 
 while (pnode != node)
 {
  ptmp = pnode->right;
  free(pnode);
  pnode = ptmp;
 }
 free(node);
}


//测试程序

#include <stdio.h>
#include <stdlib.h>
#include "dblist.h"

#define FALSE 0
#define TRUE  1

typedef unsigned int bool;

void main()
{
 int nChoose;
 int data;
 bool bFlag = FALSE;
 pdbNode pnode;
 pdbNode list = CreateList(0);
 
 while(bFlag == FALSE)
 {
  printf("Main Menu\n");
  printf("1.  Insert\n");
  printf("2.  Delete Node\n");
  printf("3.  Find\n");
  printf("4.  Length\n");
  printf("5.  Positive Print\n");
  printf("6.  Negative Print\n");
  printf("7.  Delete List\n");
  printf("0.  quit\n\n");
  
  scanf("%d", &nChoose);
  
  switch(nChoose)
  {
  case 1:
   printf("Input the data to insert:");
   scanf("%d", &data);
   list = InsertNode(list, data);
   PrintList(list);
   printf("\n");
   break;
  case 2: 
   printf("Input the data to delete: ");
   scanf("%d", &data);
   DeleteNode(list, data);
   PrintList(list);
   printf("\n");
   break;
  case 3:
   printf("Input the data to find: ");
   scanf("%d", &data);
   pnode = FindNode(list, data);
      if (NULL != pnode)
   {
    printf("Find succeed!\n");
 printf("\n");
   }
   else
   {
    printf("Find failed!\n");
 printf("\n");
   }
   break;
  case 4:
   printf("The list's length is %d\n", GetLength(list));
   printf("\n");
   break;
  case 5:
   PrintList(list);
   printf("\n");
   break;
  case 6:
   ReverPrint(list);
   printf("\n");
   break;
  case 7:
   DeleteList(list);
   printf("\n");
   break;
  case 0:
   DeleteList(list);
   bFlag = TRUE;
  }
 }
}