循环双向链表

1 简介

概念

  • 循环双向链表是一种更复杂的数据结构类型,它的节点包含指向其前一节点以及下一节点的指针。
  • 循环双向链表在任何节点中都不包含NULL。
  • 链表的最后一个节点包含列表的第一个节点的地址。
  • 链表的第一个节点还包含的前一个指针是指向最后一个节点的地址。

2 数据存储和实现

数据存储

  • 起始节点包含最后一个(也是前一个)节点的地址,即8和下一个节点,即4。链表的最后一个节点,存储在地址8并包含数据6,包含链表的第一个节点的地址

数据实现

  • 使用结构体和指针实现。
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struct node   
{
struct node *prev;
int data;
struct node *next;
}
  • 使用STL中的list实现
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#include<list>
list<int> li;

3 操作

基本操作

  • 创建
  • 遍历、搜索
  • 插入
  • 删除

实现

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#include<stdio.h>  
#include<stdlib.h>
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();
int main()
{
int choice = 0;
while (choice != 9)
{
printf("*********Main Menu*********\n");
printf("Choose one option from the following list ...\n");
printf("===============================================\n");
printf("1.Insert in Beginning\n2.Insert at last\n");
printf("3.Delete from Beginning\n4.Delete from last\n");
printf("5.Search\n6.Show\n7.Exit\n");
printf("Enter 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("OVERFLOW");
}
else
{
printf("Enter 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("Node inserted\n");
}

}
void insertion_last()
{
struct node *ptr, *temp;
int item;
ptr = (struct node *) malloc(sizeof(struct node));
if (ptr == NULL)
{
printf("OVERFLOW");
}
else
{
printf("Enter 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("node inserted\n");
}

void deletion_beginning()
{
struct node *temp;
if (head == NULL)
{
printf("UNDERFLOW");
}
else if (head->next == head)
{
head = NULL;
free(head);
printf("node 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("UNDERFLOW");
}
else if (head->next == head)
{
head = NULL;
free(head);
printf("node deleted\n");
}
else
{
ptr = head;
if (ptr->next != head)
{
ptr = ptr->next;
}
ptr->prev->next = head;
head->prev = ptr->prev;
free(ptr);
printf("node deleted\n");
}
}

void display()
{
struct node *ptr;
ptr = head;
if (head == NULL)
{
printf("nothing to print");
}
else
{
printf("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("Empty List\n");
}
else
{
printf("Enter 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");
}
}

}