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📜 数据结构-循环双链表
📅 最后修改于: 2020-10-15 00:48:22 🧑 作者: Mango
循环双链表
循环双链表是数据结构的一种更复杂的类型，其中一个节点包含指向其上一个节点以及下一个节点的指针。循环双向链表在任何节点中都不包含NULL。列表的最后一个节点包含列表的第一个节点的地址。列表的第一个节点还包含其先前指针中的最后一个节点的地址。
下图显示了一个循环的双向链表。
由于圆形双向链表在其结构中包含三部分，因此它需要每个节点更多的空间和更昂贵的基本操作。但是，圆形的双向链接列表使指针易于操作，并且搜索的效率提高了两倍。
循环双链表的内存管理
下图显示了为循环双链表分配内存的方式。变量head包含列表的第一个元素的地址，即1，因此列表的起始节点包含数据A的地址为1。由于列表的每个节点都应具有三部分，因此，列表的起始节点该列表包含最后一个节点(即8)和下一个节点(即4)的地址。列表的最后一个节点(存储在地址8处，数据为6)包含列表中第一个节点的地址，如图所示，即在循环双向链表中，最后一个节点由存储在最后一个节点的下一部分中的第一个节点的地址标识，因此包含第一个节点的地址的节点实际上是第一个节点的最后一个节点。清单。
循环双链表上的操作：
可以在循环双链表上执行各种操作。圆形双向链表的节点结构类似于双向链表。但是，下表描述了循环双链表上的操作。
| SN | Operation | Description |
|---|---|---|
| 1 | Insertion at beginning | Adding a node in circular doubly linked list at the beginning. |
| 2 | Insertion at end | Adding a node in circular doubly linked list at the end. |
| 3 | Deletion at beginning | Removing a node in circular doubly linked list from beginning. |
| 4 | Deletion at end | Removing a node in circular doubly linked list at the end. |
循环双链表中的遍历和搜索与循环单链表中的遍历和搜索相似。
C程序实现循环双链表上的所有操作
#include
#include
struct node
{
struct node *prev;
struct node *next;
int data;
};
struct node *head;
void insertion_beginning();
void insertion_last();
void deletion_beginning();
void deletion_last();
void display();
void search();
void main ()
{
int choice =0;
while(choice != 9)
{
printf("\n*********Main Menu*********\n");
printf("\nChoose one option from the following list ...\n");
printf("\n===============================================\n");
printf("\n1.Insert in Beginning\n2.Insert at last\n3.Delete from Beginning\n4.Delete from last\n5.Search\n6.Show\n7.Exit\n");
printf("\nEnter your choice?\n");
scanf("\n%d",&choice);
switch(choice)
{
case 1:
insertion_beginning();
break;
case 2:
insertion_last();
break;
case 3:
deletion_beginning();
break;
case 4:
deletion_last();
break;
case 5:
search();
break;
case 6:
display();
break;
case 7:
exit(0);
break;
default:
printf("Please enter valid choice..");
}
}
}
void insertion_beginning()
{
struct node *ptr,*temp;
int item;
ptr = (struct node *)malloc(sizeof(struct node));
if(ptr == NULL)
{
printf("\nOVERFLOW");
}
else
{
printf("\nEnter Item value");
scanf("%d",&item);
ptr->data=item;
if(head==NULL)
{
head = ptr;
ptr -> next = head;
ptr -> prev = head;
}
else
{
temp = head;
while(temp -> next != head)
{
temp = temp -> next;
}
temp -> next = ptr;
ptr -> prev = temp;
head -> prev = ptr;
ptr -> next = head;
head = ptr;
}
printf("\nNode inserted\n");
}
}
void insertion_last()
{
struct node *ptr,*temp;
int item;
ptr = (struct node *) malloc(sizeof(struct node));
if(ptr == NULL)
{
printf("\nOVERFLOW");
}
else
{
printf("\nEnter value");
scanf("%d",&item);
ptr->data=item;
if(head == NULL)
{
head = ptr;
ptr -> next = head;
ptr -> prev = head;
}
else
{
temp = head;
while(temp->next !=head)
{
temp = temp->next;
}
temp->next = ptr;
ptr ->prev=temp;
head -> prev = ptr;
ptr -> next = head;
}
}
printf("\nnode inserted\n");
}
void deletion_beginning()
{
struct node *temp;
if(head == NULL)
{
printf("\n UNDERFLOW");
}
else if(head->next == head)
{
head = NULL;
free(head);
printf("\nnode deleted\n");
}
else
{
temp = head;
while(temp -> next != head)
{
temp = temp -> next;
}
temp -> next = head -> next;
head -> next -> prev = temp;
free(head);
head = temp -> next;
}
}
void deletion_last()
{
struct node *ptr;
if(head == NULL)
{
printf("\n UNDERFLOW");
}
else if(head->next == head)
{
head = NULL;
free(head);
printf("\nnode deleted\n");
}
else
{
ptr = head;
if(ptr->next != head)
{
ptr = ptr -> next;
}
ptr -> prev -> next = head;
head -> prev = ptr -> prev;
free(ptr);
printf("\nnode deleted\n");
}
}
void display()
{
struct node *ptr;
ptr=head;
if(head == NULL)
{
printf("\nnothing to print");
}
else
{
printf("\n printing values ... \n");
while(ptr -> next != head)
{
printf("%d\n", ptr -> data);
ptr = ptr -> next;
}
printf("%d\n", ptr -> data);
}
}
void search()
{
struct node *ptr;
int item,i=0,flag=1;
ptr = head;
if(ptr == NULL)
{
printf("\nEmpty List\n");
}
else
{
printf("\nEnter item which you want to search?\n");
scanf("%d",&item);
if(head ->data == item)
{
printf("item found at location %d",i+1);
flag=0;
}
else
{
while (ptr->next != head)
{
if(ptr->data == item)
{
printf("item found at location %d ",i+1);
flag=0;
break;
}
else
{
flag=1;
}
i++;
ptr = ptr -> next;
}
}
if(flag != 0)
{
printf("Item not found\n");
}
}
}
输出：
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
1
Enter Item value123
Node inserted
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
2
Enter value234
node inserted
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
1
Enter Item value90
Node inserted
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
2
Enter value80
node inserted
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
3
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
4
node deleted
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
6
printing values ...
123
*********Main Menu*********
Choose one option from the following list ...
===============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
5
Enter item which you want to search?
123
item found at location 1
*********Main Menu*********
Choose one option from the following list ...
============================================
1.Insert in Beginning
2.Insert at last
3.Delete from Beginning
4.Delete from last
5.Search
6.Show
7.Exit
Enter your choice?
7