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【数据结构初阶】双向带头循环链表原来是纸老虎,结构复杂,操作简单


目录

​​0.结构体定义​​

​​1.初始化​​

​​2.尾插​​

​​3.打印​​

​​4.头插​​

​​5.任意位置插入前面位置​​

​​6.尾删​​

​​7.头删​​

​​8.链表长度​​

​​9.任意位置删除当前位置​​

​​10. 销毁​​

【数据结构初阶】双向带头循环链表原来是纸老虎,结构复杂,操作简单_数据结构

 

 

双向带头循环链表:结构复杂,操作简单

0.结构体定义

这里方便浏览,特地没有将int类型重命名为TLDateType 

#define _CRT_SECURE_NO_WARNINGS 1
#pragma once
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
#include<stdbool.h>

struct ListNode
{
int val;
struct ListNode* prev;
struct ListNode* next;
};

1.初始化

  1. 带头需要初始化一个哨兵位头结点
  2. 传二级指针
  3. 初始化自己的prev和next都指向自己

void ListInit(struct ListNode** pphead)
{
struct ListNode* Guard = (struct ListNode*)malloc(sizeof(struct ListNode));
if (Guard == NULL)
{
perror("ListInit");
return;
}
*pphead = Guard;
Guard->next = Guard;
Guard->prev = Guard;
}

2.尾插

  1. 一级指针
  2. 直接prev找尾
  3. 即是无首元结点,也可(头结点自环)

struct ListNode* BuyListNode(int x)
{
struct ListNode* newnode = (struct ListNode*)malloc(sizeof(struct ListNode));
if (newnode == NULL)
{
perror("BuySListNode");
return NULL;
}
newnode->val = x;
newnode->prev = NULL;
newnode->next = NULL;
return newnode;
}

void ListPushBack(struct ListNode* phead,int x)
{
assert(phead);
struct ListNode* newnode = BuyListNode(x);

struct ListNode* tail = phead->prev;

newnode->next = phead;
phead->prev = newnode;

tail->next = newnode;
newnode->prev = tail;
}

3.打印

  1. 可assert断言(建议单链表不用断言)---头结点
  2. 起始条件cur=phead->next;
  3. 循环终止条件cur==phead

void ListPrint(struct ListNode* phead)
{
assert(phead);
struct ListNode* cur = phead->next;
while (cur != phead)
{
printf("%d->", cur->val);
cur = cur->next;
}
printf("NULL\n");
}

4.头插

  1. 一级指针
  2. 即是无首元结点,也可(头结点自环)

void ListPushFront(struct ListNode* phead,int x)
{
assert(phead);
struct ListNode* newnode = BuyListNode(x);

struct ListNode* next = phead->next;

newnode->next = next;
next->prev = newnode;

phead->next = newnode;
newnode->prev = phead;

}

5.任意位置插入前面位置

  1. 因为有prev,前插不同phead
  2. 尾插,头插就用ListInsert传不同pos参数
  3. 如果pos传phead,就相当于于是尾插
  4. 如果pos传phead->next,就相当于于是头插

void ListInsert(struct ListNode* pos, int x)
{
assert(pos);
struct ListNode* newnode = BuyListNode(x);
struct ListNode* prev = pos->prev;

prev->next = newnode;
newnode->prev = prev;

newnode->next = pos;
pos->prev = newnode;
}

头插:ListNode(phead->next,x);
尾插:ListNode(phead,x);

6.尾删

  1. 不为空,!ListEmpty(plhead)
  2. prev,tail,phead

bool ListEmpty(struct ListNode* phead)
{
return phead->next == phead;
}

void ListPopBack(struct ListNode* phead)
{
assert(phead);
assert(!ListEmpty(phead));
struct ListNode* tail = phead->prev;
struct ListNode* prev = tail->prev;

prev->next = phead;
phead->prev = prev;
free(tail);
tail = NULL;
}

7.头删

  1. 不为空,!ListEmpty(plhead)
  2. phead,first,second

void ListPopFront(struct ListNode* phead)
{
assert(phead);
assert(!ListEmpty(phead));

struct ListNode* first = phead->next;
struct ListNode* second = first->next;

phead->next = second;
second->prev = phead;
free(first);
first = NULL;
}

8.链表长度

  1. 起始条件:cur=phead->next
  2. 终止条件:cur!=phead;

size_t ListSize(struct ListNode* phead)
{
size_t size = 0;
struct ListNode* cur = phead->next;
while (cur != phead)
{
++size;
cur = cur->next;
}
return size;
}

9.任意位置删除当前位置

  1. 不为空,!ListEmpty(plhead)
  2. 尾删,头删就用ListErase传不同pos参数
  3. 如果pos传phead->prev,就是尾删
  4. 如果pos传phead->next,就是头删

void ListErase(struct ListNode* pos)
{
assert(pos);
struct ListNode* prev = pos->prev;
struct ListNode* next = pos->next;

prev->next = next;
next->prev = prev;

free(pos);
pos = NULL;
}

10. 销毁

  1. 看是否保留哨兵头,来传一级或二级指针
  2. 先保留哨兵头作为判断循环条件,最后决定是否释放哨兵头

void ListDestory(struct ListNode** pphead)
{
assert(pphead);
struct ListNode* cur = (*pphead)->next;
while (cur != *pphead)
{
struct ListNode* next = cur->next;
free(cur);
cur = next;
}
free(*pphead);
*pphead = NULL;
}

制作不易,敬请三连

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