【数据结构】双向带头循环链表实现及总结

简单不先于复杂，而是在复杂之后。

文章目录

- - 1. 双向带头循环链表的实现
  - 2. 顺序表和链表的区别

1. 双向带头循环链表的实现

List.h

#pragma once
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <stdbool.h>typedef int LTDataType;typedef struct ListNode
{struct ListNode* next;struct ListNode* prev;LTDataType data;
}LTNode;//初始化
LTNode* ListInit();//打印
void ListPrint(LTNode* phead);//尾插
void ListPushBack(LTNode* phead, LTDataType x);//头插
void ListPushFront(LTNode* phead, LTDataType x);//尾删
void ListPopBack(LTNode* phead);//头删
void ListPopFront(LTNode* phead);//链表判空
bool ListEmpty(LTNode* phead);//链表长度
size_t ListSize(LTNode* phead);//遍历查找(也可以充当修改的功能，所以链表不需要单独实现修改的功能)
LTNode* ListFind(LTNode* phead, LTDataType x);//pos之前插入
void ListInsert(LTNode* pos, LTDataType x);//删除pos位置
void ListErase(LTNode* pos);//链表销毁
void ListDestory(LTNode* phead);

List.c

#define _CRT_SECURE_NO_WARNINGS 1
#include"List.h"LTNode* ListInit()
{LTNode* guard = (LTNode*)malloc(sizeof(LTNode));if (guard == NULL){perror("malloc fail");exit(-1);}guard->next = guard;guard->prev = guard;return guard;
}LTNode* BuyListNode(LTDataType x)
{LTNode* Node = (LTNode*)malloc(sizeof(LTNode));if (Node == NULL){perror("malloc fail");exit(-1);}Node->next = NULL;Node->prev = NULL;Node->data = x;return Node;}void ListPrint(LTNode* phead)
{assert(phead);printf("phead<=>");LTNode* cur = phead->next;while (cur != phead){printf("%d<=>", cur->data);cur = cur->next;}printf("\n");
}void ListPushBack(LTNode* phead, LTDataType x)
{assert(phead);/*LTNode* newnode = BuyListNode(x);LTNode* tail = phead->prev;tail->next = newnode;newnode->prev = tail;phead->prev = newnode;newnode->next = phead;*/ListInsert(phead, x);//双向带头循环链表不需要专门写头插尾插//只需要复用ListInsert的代码即可
}void ListPushFront(LTNode* phead, LTDataType x)
{assert(phead);//LTNode* newnode = BuyListNode(x);//先链接newnode和phead->next节点之间的关系//newnode->next = phead->next;//phead->next->prev = newnode;//phead->next = newnode;//newnode->prev = phead;//如果不想关心顺序LTNode* first = phead->next;phead->next = newnode;newnode->prev = phead;newnode->next = first;first->prev = newnode;ListInsert(phead->next, x);
}void ListPopBack(LTNode* phead)
{assert(phead);assert(!ListEmpty(phead));/*LTNode* tail = phead->prev;LTNode* prev = tail->prev;prev->next = phead;phead->prev = prev;free(tail);tail = NULL;*/ListErase(phead->prev);
}void ListPopFront(LTNode* phead)
{assert(phead);assert(!ListEmpty(phead));/*LTNode* first = phead->next;LTNode* second = first->next;phead->next = second;second->prev = phead;free(first);first = NULL;*/ListErase(phead->next);
}bool ListEmpty(LTNode* phead)
{assert(phead);return phead->next == phead;
}size_t ListSize(LTNode* phead)
{assert(phead);size_t n = 0;LTNode* cur = phead->next;while (cur != phead){++n;cur = cur->next;}return n;
}LTNode* ListFind(LTNode* phead, LTDataType x)
{assert(phead);size_t n = 0;LTNode* cur = phead->next;while (cur != phead){if (cur->data == x){return cur;}}
}void ListInsert(LTNode* pos, LTDataType x)
{assert(pos);LTNode* prev = pos->prev;LTNode* newnode = BuyListNode(x);//prev newnode pos 链接prev->next = newnode;newnode->prev = prev;newnode->next = pos;pos->prev = newnode;
}void ListErase(LTNode* pos)
{assert(pos);LTNode* prev = pos->prev;LTNode* next = pos->next;prev->next = next;next->prev = prev;free(pos);//pos = NULL;
}//可以传二级指针，内部置空头结点
//建议：也可以考虑一级指针，让调用 ListDestory 的人置空（可以保持接口一致性）
void ListDestory(LTNode* phead)
{assert(phead);LTNode* cur = phead->next;while (cur != phead){LTNode* next = cur->next;free(cur);cur = next;}free(phead);//phead = NULL;
}

Test.c

#define _CRT_SECURE_NO_WARNINGS 1
#include"List.h"void TestList1()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPushBack(plist, 4);ListPrint(plist);ListPushFront(plist, 10);ListPushFront(plist, 20);ListPushFront(plist, 30);ListPushFront(plist, 40);ListPrint(plist);ListPopBack(plist);ListPopBack(plist);ListPopBack(plist);ListPopBack(plist);ListPrint(plist);}void TestList2()
{LTNode* plist = ListInit();ListPushBack(plist, 1);ListPushBack(plist, 2);ListPushBack(plist, 3);ListPushBack(plist, 4);ListPrint(plist);ListPopFront(plist);ListPopFront(plist);ListPrint(plist);ListPopFront(plist);ListPopFront(plist);ListPrint(plist);}int main()
{TestList2();return 0;
}

2. 顺序表和链表的区别

不同点	顺序表	链表
存储空间	物理上一定连续	逻辑上连续，但物理上不一定连续
随机访问	支持 O(1)	不支持 O(N)
任意位置插入或删除元素	可能需要搬移元素，效率低 O(N)	只需修改指针指向
插入	动态顺序表，空间不够时需要扩容	没有容量的概念
应用场景	元素高效存储+频繁访问	任意位置插入和删除频繁
缓存利用率	高	低

备注：缓存利用率参考存储体系结构以及局部原理性。

顺序表优点：

尾插尾删效率很高。
随机访问。（用下标访问）’
相比链表结构：cpu高速缓存命中率更高。

顺序表缺点：

头部和中部插入删除效率低。 —O(N)
扩容。性能消耗+空间浪费

链表优点：

任意位置插入删除效率很高。 O(1)
按需申请释放。

链表缺点：

不支持随机访问