作者：一个喜欢猫咪的的程序员

专栏：《数据结构》

喜欢的话：世间因为少年的挺身而出，而更加瑰丽。                                  ——《人民日报》

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目录

带头双向循环链表

List.h

List.c

Test.c

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带头双向循环链表

本篇我们来介绍一个结构比较复杂的链表——带头双向循环链表

它的结构看上去十分复杂但代码实现这个链表确实很简单的。 

如果对其中函数实现思想不太懂的话可以看看我的另外一篇博客：

t.csdn.cn/47qGshttp://t.csdn.cn/47qGs

List.h

#pragma once
#include<stdio.h>
#include<assert.h>
#include<stdlib.h>
#include<stdbool.h>
typedef int LTDateType;
typedef struct ListNode
{
	struct ListNode* prev;
	LTDateType date;
	struct ListNode* next;
}LTNode;
LTNode* BuyListNode(LTDateType x);
LTNode* LTInit();
void LTPrint(LTNode* phead);
void LTPushBack(LTNode* phead, LTDateType x);
void LTPopBack(LTNode* phead);
void LTPushFront(LTNode* phead, LTDateType x);
void LTPopFront(LTNode* phead);
LTNode* LTFind(LTNode* phead, LTDateType x);
void LTInsert(LTNode* pos, LTDateType x);
void LTErase(LTNode* pos);
bool LTEmpty(LTNode*phead);
size_t LTSize(LTNode* phead);
void LTDestroy(LTNode* phead);

List.c

#include"List.h"
LTNode* BuyListNode(LTDateType x)
{
	LTNode* node = (LTNode*)malloc(sizeof(LTNode));
	if (node == NULL)
	{
		perror("malloc fail");
		exit(-1);
	}
	node->date = x;
	node->next = NULL;
	node->prev = NULL;
	return node;
}
LTNode* LTInit()
{
	LTNode*phead = BuyListNode(-1);
	phead->next = phead;
	phead->prev = phead;
	return phead;
}
void LTPushBack(LTNode* phead, LTDateType x)
{
	assert(phead);
	/*LTNode* newnode = BuyListNode(x);
	LTNode* tail = phead->prev;
	tail->next = newnode;
	newnode->prev = tail;
	phead->prev = newnode;
	newnode->next = phead;*/
	LTInsert(phead, x);
}
void LTPopBack(LTNode* phead)
{
	assert(phead);
	assert(phead->next != phead);
	/*LTNode* tail = phead->prev;
	LTNode* tailPrev = tail->prev;
	tailPrev->next = phead;
	phead->prev = tailPrev;
	free(tail);*/
	LTErase(phead->prev);
}
void LTPushFront(LTNode* phead, LTDateType x)
{
	/*LTNode* newnode = BuyListNode(x);
	LTNode* cur = phead->next;
	phead->next = newnode;
	newnode->prev = phead;
	newnode->next = cur;
	cur->prev = newnode;*/
	LTInsert(phead->next, x);
}
void LTPrint(LTNode* phead)
{
	assert(phead);
	LTNode* cur = phead->next;
	while (cur!=phead)
	{
		printf("%d->", cur->date);
		cur = cur->next;
	}
	printf("\n");
}
void LTPopFront(LTNode* phead)
{
	assert(phead);
	assert(phead->next != phead);
	//LTNode* first = phead->next;
	//LTNode* second = first->next;
	//phead->next = second;
	//second->prev = phead;
	//free(first);
	LTErase(phead->next);
}
LTNode* LTFind(LTNode* phead, LTDateType x)
{
	assert(phead);
	LTNode* cur = phead->next;
	while (cur != phead)
	{
		if (cur->date == x)
			return cur;
		cur = cur->next;
	}
	return NULL;
}
void LTInsert(LTNode* pos, LTDateType x)
{
	assert(pos);
	LTNode* newnode = BuyListNode(x);
	LTNode* front = pos->prev;
	front->next = newnode;
	newnode->prev = front;
	pos->prev = newnode;
	newnode->next = pos;
}
void LTErase(LTNode* pos)
{
	assert(pos);
	LTNode* prev = pos->prev;
	LTNode* next = pos->next;
	free(pos);
	prev->next = next;
	next->prev = prev;
}
bool LTEmpty(LTNode* phead)
{
	assert(phead);
	return phead == phead->next;
}
size_t LTSize(LTNode* phead)
{
	assert(phead);

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

void LTDestroy(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

#include"List.h"
void test1()
{
	LTNode* phead = LTInit();
	LTPushBack(phead,1);
	LTPushBack(phead, 2);
	LTPushBack(phead, 3);
	LTPushBack(phead, 4);
	LTPrint(phead);
	LTPopBack(phead);
	//LTPopBack(phead);
	//LTPopBack(phead);
	/*LTPopBack(phead);*/
	LTPrint(phead);
	LTPushFront(phead,10);
	LTPrint(phead);
	LTPopFront(phead);
	LTPrint(phead);
}
void test2()
{
	LTNode* phead = LTInit();
	LTPushBack(phead, 1);
	LTPushBack(phead, 2);
	LTPushBack(phead, 3);
	LTPushBack(phead, 4);
	LTPrint(phead);
	LTNode* pos = LTFind(phead, 3);
	if (pos)
	{
		pos->date = pos->date * 10;
		LTPrint(phead);
	}
	LTPushFront(phead, 10);
	LTPrint(phead);
}
int main()
{
	test2();
	return 0;
}