[数据结构与算法](C语言)实现带头双向循环链表的接口

各函数功能如下

申请空间

ListNode* BuyListNode(LTDataType x)
{
	ListNode* node = (ListNode*)malloc(sizeof(ListNode));
	node->next = NULL;
	node->prev = NULL;
	node->data = x;
	return node;
}

初始化

ListNode* ListInit()
{
	ListNode* phead = BuyListNode(0);
	phead->next = phead;
	phead->prev = phead;

	return phead;
}

指定位置插入

void ListInsert(ListNode* pos, LTDataType x)
{
	assert(pos);

	ListNode* prev = pos->prev;
	ListNode* newnode = BuyListNode(x);
	prev->next = newnode;
	newnode->prev = prev;
	newnode->next = pos;
	pos->prev = newnode;
}

头插

void ListPushFront(ListNode* phead, LTDataType x)
{
	//assert(phead);
	//ListNode* first = phead->next;
	//ListNode* newnode = BuyListNode(x);
	phead newnode first
	//phead->next = newnode;
	//newnode->prev = phead;
	//newnode->next = first;
	//first->prev = newnode;


	ListInsert(phead->next, x);//实现了指定位置插入后，可以套用
}

尾插

void ListPushBack(ListNode* phead, LTDataType x)
{
	//assert(phead);
	//ListNode* tail = phead->prev;
	//ListNode* newnode = BuyListNode(x);

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

	ListInsert(phead, x);
}

指定位置删除

void ListErase(ListNode* pos)
{
	assert(pos);

	ListNode* prev = pos->prev;
	ListNode* next = pos->next;

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

	free(pos);
}

头删

void ListPopFront(ListNode* phead)
{
	//assert(phead);
	//assert(phead->next != phead);

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

	//free(first);

	//phead->next = second;
	//second->prev = phead;

	ListErase(phead->next);
}

尾删

void ListPopBack(ListNode* phead)
{
	//assert(phead);
	//assert(phead->next != phead);

	//ListNode* tail = phead->prev;
	//ListNode* tailPrev = tail->prev;
	//free(tail);

	//tailPrev->next = phead;
	//phead->prev = tailPrev;

	ListErase(phead->prev);

}

查找

ListNode* ListFind(ListNode* phead, LTDataType x)
{
	assert(phead);

	ListNode* cur = phead->next;
	while (cur)
	{
		if (cur->data == x)
		{
			return cur;
		}
		cur = cur->next;
	}

	return NULL;
}

判空

int ListEmpty(ListNode* phead)
{
	assert(phead);
	return phead->next == phead ? 1 : 0;
}

元素个数

int ListSize(ListNode* phead)
{
	assert(phead);

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

链表销毁

void ListDestory(ListNode* phead)
{
	assert(phead);

	ListNode* cur = phead->next;
	while (cur != phead)
	{
		ListNode* next = cur->next;
		free(cur);
		cur = next;
	}

	free(phead);
	phead = NULL;
}

List.h

#pragma once
#define _CRT_SECURE_NO_WARNINGS 1

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

typedef int LTDataType;
typedef struct ListNode
{
	struct ListNode* next;
	struct ListNode* prev;
	LTDataType data;
}ListNode;

//打印
void ListPrint(ListNode* phead);

//申请空间
ListNode* BuyListNode(LTDataType x);

//初始化
ListNode* ListInit();

//尾插
void ListPushBack(ListNode* phead, LTDataType x);

//头插
void ListPushFront(ListNode* phead, LTDataType x);

//尾删
void ListPopBack(ListNode* phead);

//头删
void ListPopFront(ListNode* phead);

//查找
ListNode* ListFind(ListNode* phead, LTDataType x);

//插入
void ListInsert(ListNode* pos, LTDataType x);

//删除
void ListErase(ListNode* pos);

//空返回1，非空返回0
int ListEmpty(ListNode* phead);

//元素个数
int ListSize(ListNode* phead);

//链表销毁
void ListDestory(ListNode* phead);

List.c

#include "List.h"

ListNode* BuyListNode(LTDataType x)
{
	ListNode* node = (ListNode*)malloc(sizeof(ListNode));
	node->next = NULL;
	node->prev = NULL;
	node->data = x;
	return node;
}



ListNode* ListInit()
{
	ListNode* phead = BuyListNode(0);
	phead->next = phead;
	phead->prev = phead;

	return phead;
}

//打印
void ListPrint(ListNode* phead)
{
	ListNode* cur = phead->next;
	while (cur != phead)
	{
		printf("%d ", cur->data);
		cur = cur->next;
	}
	puts("\n------------------------------------------------\n");
}


void ListPushBack(ListNode* phead, LTDataType x)
{
	//assert(phead);
	//ListNode* tail = phead->prev;
	//ListNode* newnode = BuyListNode(x);

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

	ListInsert(phead, x);
}


//头插
void ListPushFront(ListNode* phead, LTDataType x)
{
	//assert(phead);
	//ListNode* first = phead->next;
	//ListNode* newnode = BuyListNode(x);
	phead newnode first
	//phead->next = newnode;
	//newnode->prev = phead;
	//newnode->next = first;
	//first->prev = newnode;


	ListInsert(phead->next, x);
}



//尾删
void ListPopBack(ListNode* phead)
{
	//assert(phead);
	//assert(phead->next != phead);

	//ListNode* tail = phead->prev;
	//ListNode* tailPrev = tail->prev;
	//free(tail);

	//tailPrev->next = phead;
	//phead->prev = tailPrev;

	ListErase(phead->prev);

}

//头删
void ListPopFront(ListNode* phead)
{
	//assert(phead);
	//assert(phead->next != phead);

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

	//free(first);

	//phead->next = second;
	//second->prev = phead;

	ListErase(phead->next);
}

//查找
ListNode* ListFind(ListNode* phead, LTDataType x)
{
	assert(phead);

	ListNode* cur = phead->next;
	while (cur)
	{
		if (cur->data == x)
		{
			return cur;
		}
		cur = cur->next;
	}

	return NULL;
}

//插入
void ListInsert(ListNode* pos, LTDataType x)
{
	assert(pos);

	ListNode* prev = pos->prev;
	ListNode* newnode = BuyListNode(x);
	prev->next = newnode;
	newnode->prev = prev;
	newnode->next = pos;
	pos->prev = newnode;
}

//删除
void ListErase(ListNode* pos)
{
	assert(pos);

	ListNode* prev = pos->prev;
	ListNode* next = pos->next;

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

	free(pos);
}


//空返回1，非空返回0
int ListEmpty(ListNode* phead)
{
	assert(phead);
	return phead->next == phead ? 1 : 0;
}


int ListSize(ListNode* phead)
{
	assert(phead);

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

void ListDestory(ListNode* phead)
{
	assert(phead);

	ListNode* cur = phead->next;
	while (cur != phead)
	{
		ListNode* next = cur->next;
		free(cur);
		cur = next;
	}

	free(phead);
	phead = NULL;
}

test.c

#include "List.h"


void TestList1()
{
	ListNode* plist = ListInit();
	ListPushBack(plist, 1);
	ListPushBack(plist, 2);
	ListPushBack(plist, 3);
	ListPushBack(plist, 4);
	ListPrint(plist);


	ListPushFront(plist, 0);
	ListPushFront(plist, -1);
	ListPushFront(plist, -2);
	ListPrint(plist);

	ListPopFront(plist);
	ListPopFront(plist);
	ListPopFront(plist);
	ListPrint(plist);


	ListDestory(plist);
	plist = NULL;
}


int main()
{
	TestList1();
	return 0;
}

总结

链表优点：

1. 按需申请内存，需要存一个数据，就申请一块内存。不存在空间浪费。
2. 任意位置O(1)时间内插入删除数据

链表缺点：

1. 不支持下标的随机访问
2. 缓存命中率相对低。

顺序表优点

1. 按下标去进行随机访问
2. cpu高速缓存命中率比较高

顺序表缺点

1. 空间不够需要增容。（一定程序的性能消耗），可能存在一定的空间浪费
2. 头部或者中间插入删除数据，需要挪动数据，效率比较低->O(N)