【数据结构】双向链表

#pragma once
#include<stdio.h>
#include<stdlib.h>
#include<assert.h>
#include<stdbool.h>
typedef int LTDataType;
typedef struct ListNode
{
	struct ListNode* next;
	struct ListNode* prev;
	LTDataType data;
}LTNode;
LTNode* ListInit();
void ListPrint(LTNode* phead);
void ListPushBack(LTNode* phead, LTDataType x);
void ListPushFront(LTNode* phead, LTDataType x);
void ListPopBack(LTNode* phead);
void ListPopFront(LTNode* phead);
bool ListEmpty(LTNode* phead);
size_t ListSize(LTNode* phead);
LTNode* ListFind(LTNode* phead, LTDataType x);
//在pos之前插入
void ListInsert(LTNode* pos, LTDataType x);
//删除pos位置
void ListErase(LTNode* pos);
void ListDestory(LTNode* phead);

LTNode* BuyListNode(LTDataType x)
{
	LTNode* node = (LTNode*)malloc(sizeof(LTNode));
	if (node == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}
	node->next = NULL;
	node->prev = NULL;
}

LTNode* ListInit()
{
	LTNode* guard = (LTNode*)malloc(sizeof(LTNode));
	if (guard == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}
	guard->next = guard;
	guard->prev = guard;
	return guard;
}

void ListPrint(LTNode* phead)
{
	assert(phead);
	printf("guard<=>");
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		printf("%d<=>", cur->data);
		cur = cur->next;
	}
	printf("\n");
}

//可以传二级 内部置空头结点
//建议:也可以考虑使用一级指针 让调用ListDestory的人将其置空 保持接口的一致性
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;
}

void ListPushBack(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* newnode = BuyListNode(x);
	LTNode* tail = phead->prev;
	tail->next = newnode;
	newnode->prev = tail;
	newnode->next = phead;
	phead->prev = newnode;
}

void ListPopBack(LTNode* phead)
{
	assert(phead);
	//链表为空返回true 取反为假就报错
	assert(!ListEmpty(phead));
	//删掉最后一个结点 哨兵位变成自己指向自己 代码依然成立
	LTNode* tail = phead->prev;
	LTNode* prev = tail->prev;
	prev->next = phead;
	phead->prev = prev;
	free(tail);
	tail = NULL;
}

void ListPushFront(LTNode* phead, LTDataType x)
{
	assert(phead);
	//先链接newnode和phead->next结点之间的关系
	/*LTNode* newnode = BuyListNode(x);
	newnode->next = phead->next;
	phead->next->prev = newnode;
	phead->next = newnode;
	newnode->prev = phead;*/
	//不关心先后顺序
	LTNode* newnode = BuyListNode(x);
	LTNode* first = phead->next;
	phead->next = newnode;
	newnode->prev = phead;
	newnode->next = first;
	first->prev = newnode;
}

void ListPopFront(LTNode* phead)
{
	assert(phead);
	//链表为空返回true 取反为假就报错
	assert(!ListEmpty(phead));
	//删到剩最后一个结点时 first指向最后一个结点 second指向哨兵位结点 删到最后哨兵位自己指向自己 代码依然成立
	LTNode* first = phead->next;
	LTNode* second = first->next;
	phead->next = second;
	second->prev = phead;
	free(first);
	first = NULL;
}

//双向链表的查找可以替代其修改函数
LTNode* ListFind(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		if (cur->data == x)
		{
			return cur;
		}
		cur = cur->next;
	}
	return NULL;
}

//在pos之前插入
void ListInsert(LTNode* pos, LTDataType x)
{
	assert(pos);
	LTNode* prev = pos->prev;
	LTNode* newnode = BuyListNode(x);
	//prev newnode pos
	prev->next = newnode;
	newnode->prev = prev;
	newnode->next = pos;
	pos->prev = newnode;
}
//ListInsert(phead,x)代替尾插
//ListInsert(phead->next,x)代替头插

//删除pos位置
void ListErase(LTNode* pos)
{
	assert(pos);
	LTNode* prev = pos->prev;
	LTNode* next = pos->next;
	prev->next = next;
	next->prev = prev;
	free(pos);
	//pos = NULL;置空并不起作用
}
//ListErase(phead->prev)代替尾删
//ListErase(phead->next)代替头删

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;
}