双链表操作

//------------------------------------------------------------------------------
// 双链表的相关操作
//------------------------------------------------------------------------------
#include <iostream>
using namespace std;

// 双链表数据结构
typedef struct DNode
{
	int data;
	DNode* prev;
	DNode* next;

}DoubleList, *pDoubleList;

//******************************************************************************
// Name: CreateNode
// Desc: 创建双链表
//******************************************************************************
DNode* CreateDNode()
{
	DNode* head;
	DNode* tempPrev;
	DNode* tempNext;
	head = new DNode;
	head->next = NULL;
	head->prev = NULL;
	tempPrev   = NULL;
	tempNext   = head;

	cout<<"please input some datas to create a doubleNode:"<<endl;
	int data;
	while(cin>>data)
	{
		// 赋值后继
		tempNext->next = new DNode;
		tempNext	  = tempNext->next;
		tempNext->data = data;

		// 赋值前驱
		tempNext->next = NULL;
		tempNext->prev = tempPrev;
		tempPrev      = tempNext;
	}

	head = head->next;
	head->prev = NULL;

	return head;

}

//******************************************************************************
// Name: DNodeLength
// Desc: 计算双链表的长度
//******************************************************************************
int DNodeLength(DNode* head)
{
	if(head == NULL) return 0;

	DNode* currentDNode = head;
	int	   currentLength = 0;
	while(currentDNode != NULL)
	{
		++currentLength;
		currentDNode = currentDNode->next;
	}

	return currentLength;
}

//******************************************************************************
// Name: PrintDNode
// Desc: 打印双链表
//******************************************************************************
void PrintDNode(DNode* head)
{
	if(head == NULL)	
	{
		cout<<"链表元素为空"<<endl;
	}
	else
	{
		DNode* currentDNode = head;
		while(currentDNode != NULL)
		{
			cout<<currentDNode->data<<" ";
			currentDNode = currentDNode->next;
		}
		cout<<endl;
	}
}

//******************************************************************************
// Name: 删除双链表中的元素
// Desc: DeleteDNode(DNode* head, int data)
//******************************************************************************
DNode* DeleteDNode(DNode* head, int data)
{
	if(head == NULL) 
	{
		cout<<"链表为空!"<<endl;
		return NULL;
	}
	else
	{
		DNode* currentNode = head;

		// 试图找到要删除的元素
		while(currentNode != NULL 
			&& currentNode->data != data)
		{	
			currentNode = currentNode->next;
		}

		if(currentNode->prev != NULL)			// 有前驱
		{
			if(currentNode->next != NULL)		// 有前驱，有后继，删除中间元素
			{
				currentNode->prev->next = currentNode->next;
				currentNode->next->prev = currentNode->prev;
			}
			else								// 有前驱，无后继，删除最后一个元素
			{
				currentNode->prev->next = NULL;
				currentNode->prev = NULL;
			}
		}
		else									// 无前驱
		{
			if(currentNode->next != NULL)		// 无前驱，有后继，删除第一个元素
			{
				head = head->next;				// 改变了头指针地址
				currentNode->next->prev = NULL;
			}
			else								// 无前驱，无后继，删除唯一元素
			{
				head = NULL;					// 此处不能进行delete head操作，因为下面会删除，删除两次会有问题
			}
		}

		delete currentNode;
		currentNode = NULL;

		return head;
	}
}

//******************************************************************************
// Name: InsertDNode
// Desc: 双链表中插入元素,参数为位置和要插入的值
//******************************************************************************
DNode* InsertDNode(DNode* head, int pos, int data)
{
	DNode* newDNode   = new DNode;		        // 待插入的新节点
	newDNode->data = data;
	newDNode->next = NULL;
	newDNode->prev = NULL;

	DNode* rightDNode = head;                   // 将在这个位置的前面插入
	int	   maxPos	  = DNodeLength(head)    ;  // 双链表长度

	if(head == NULL)	
	{
		return newDNode;
	}

	if(pos > maxPos)						  // 如果越界，则插在最尾部
	{
		pos = maxPos ;
	}


	for(int i = 1; i < pos; ++i)
	{
		rightDNode = rightDNode->next;
	}

	if(0 == pos || maxPos == pos)			 // 插在头部和插在尾部的单独处理
	{
		if(pos > 0)							 // 尾部
		{
			rightDNode->next = newDNode;
			newDNode->prev = rightDNode;
			newDNode->next = NULL;
		}
		else								 // 头部
		{
			newDNode->next = rightDNode;
			newDNode->prev = NULL;
			rightDNode->prev = newDNode;
			head = newDNode;				// 改变了头指针地址
		}
	}
	else									 // 插在中间的元素
	{
		rightDNode->prev->next = newDNode;
		newDNode->prev = rightDNode->prev;

		rightDNode->prev = newDNode;
		newDNode->next = rightDNode;
	}

	return head;
}


int main()
{
	int deleteElem;		// 要删除的元素
	int addPos;			// 插入的位置
	int addElem;		// 添加的元素

	cout<<"创建双链表:"<<endl;
	DNode* head = CreateDNode();
	cout<<"--------------------------------------------------------"<<endl;
	cout<<"双链表长度为: "<<DNodeLength(head)<<endl;
	cout<<"--------------------------------------------------------"<<endl;
	cout<<"打印双链表: "<<endl;
	PrintDNode(head);
	cout<<"--------------------------------------------------------"<<endl;

	cout<<"请输入要删除的元素:"<<endl;
	cin.clear();		// 创建双链表的时候，已经暂用了IO缓冲
	cin>>deleteElem;
	head = DeleteDNode(head, deleteElem);
	cout<<"--------------------------------------------------------"<<endl;
	cout<<"打印双链表: "<<endl;
	PrintDNode(head);
	cout<<"--------------------------------------------------------"<<endl;
	
	cout<<"请输入插入元素的位置和要插入的元素"<<endl;
	cin>>addPos>>addElem;
	head = InsertDNode(head, addPos, addElem);
	cout<<"--------------------------------------------------------"<<endl;
	cout<<"打印双链表: "<<endl;
	PrintDNode(head);
	cout<<"--------------------------------------------------------"<<endl;

	system("pause");
	return 0;
}