数据结构与算法——双向链表

函数的声明

//结构的定义
typedef int LTDataType;
typedef struct ListNode {
	LTDataType data;
	struct ListNode* next;
	struct ListNode* prev;
}LTNode;

//初始化(法一)
void LTInit(LTNode** pphead);
//法二:
//LTNode* LTInit();

函数的实现

#include"List.h"

//申请空间
LTNode* LTBuyNode(LTDataType x)
{
	LTNode* newnode = (LTNode*)malloc(sizeof(LTNode));
	if (newnode == NULL)
	{
		perror("malloc fail!");
		exit(1);
	}
	newnode->data = x;
	newnode->next = newnode->prev = newnode;

	return newnode;
}

//初始化(法一)
void LTInit(LTNode** pphead)
{
	assert(pphead);
	*pphead = LTBuyNode(-1);
}

/*法二
LTNode* LTInit()
{
	LTNode* phead = LTBuyNode(-1);
	return phead;//返回双向链表的头结点
}*/

函数的测试

#include"List.h"

void test01()
{  //法一：
	LTNode* plist = NULL;//单链表为空时，指向第一个节点的指针为空
	                     //双链表为空时，链表中只有一个头结点！
	LTInit(&plist);
	/*法二：
	LTNode* plist = LTInit();
	*/
}

int main()
{
	test01();
	return 0;
}

//打印
void LTPrint(LTNode* phead)
{
	LTNode* pcur = phead->next;
	while (pcur != phead) //将哨兵位的下一个结点定为pcur，向后遍历，停止的标志为pcur = phead
	{
		printf("%d -> ", pcur->data);
		pcur = pcur->next;
	}
	printf("\n");
}

//尾插
void LTPushBack(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* newnode = LTBuyNode(x);
	newnode->prev = phead->prev;
	newnode->next = phead;

	phead->prev->next= newnode;

	phead->prev = newnode;
}

//头插
void LTPushFront(LTNode* phead, LTDataType x)
{
	assert(phead);
	LTNode* newnode = LTBuyNode(x);
	newnode->next = phead->next;
	newnode->prev = phead;

	phead->next->prev = newnode;

	phead->next = newnode;
}

//判断链表是否为空:只有一个头结点，记得在头文件声明
bool LTEmpty(LTNode* phead)
{
	assert(phead);
	return phead->next == phead;
} // 返回true为空，反回flase不为空

//尾删
void LTPopBack(LTNode* phead)
{
	assert(!LTEmpty(phead));
	LTNode* del = phead->prev;

	del->prev->next = phead;
	phead->prev = del->prev;

	free(del);
	del = NULL;
}

//判断链表是否为空:只有一个头结点
bool LTEmpty(LTNode* phead)
{
	assert(phead);
	return phead->next == phead;
} // 返回true为空，反回flase不为空

//头删
void LTPopFront(LTNode* phead)
{
	assert(!LTEmpty(phead));
	LTNode* del = phead->next;

	del->next->prev = phead;
	phead->next = del->next;

	free(del);
	del = NULL;

}

以上时间复杂度全是O(1),不需要遍历

//查找，记得添加到头文件
LTNode* LTFind(LTNode* phead, LTDataType x)
{
	LTNode* pcur = phead->next;
	while (pcur != phead)
	{
		if (pcur->data == x)
		{
			return pcur;
		}
		pcur = pcur->next;
	}
	return NULL;
}

//在pos位置后插入结点
void LTInsertBack(LTNode* pos, LTDataType x)
{
	assert(pos);
	LTNode* newnode = LTBuyNode(x);

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

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

//在pos位置前插入结点
void LTInsertFront(LTNode* pos, LTDataType x)
{
	assert(pos);
	LTNode* newnode = LTBuyNode(x);

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

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

//删除pos位置的结点
void LTErase(LTNode* pos)
{
	assert(pos);
	pos->next->prev = pos->prev;
	pos->prev->next = pos->next;

	free(pos);
	pos = NULL;
}

//链表的销毁，因为形参会影响实参，所以传二级指针
void LTDestroy(LTNode** pphead)
{
	LTNode* pcur = (*pphead)->next;
	while (pcur != *pphead)
	{
		LTNode* next = pcur->next;
		free(pcur);
		pcur = next;
	}
	free(*pphead);
	*pphead = NULL;
}

void test01()
{
	LTDestroy(&plist);
}

void LTDestroy(LTNode* phead)
{
	LTNode* pcur = phead->next;
	while (pcur != phead)
	{
		LTNode* next = pcur->next;
		free(pcur);
		pcur = next;
	}
	free(phead);
	phead = NULL;
}

void test01()
{
	LTDestroy(plist);
	plist = NULL;
}