二元查找树转换成双向链表

输入一颗二元查找树，将该二元查找树转换成一个排序的双向链表，要求不能创建任何新的结点，只调整指针的指向。

　比如将二元查找树

转换成双向链表4=6=8=10=12=14=16。

#include<iostream>
using namespace std;
struct BSTreeNode
{
	int m_nValue;
	BSTreeNode *m_pleft;
	BSTreeNode *m_pright;
};


void addBSTreeNode(BSTreeNode *&pCurrent,int value);
void inOrderBSTree(BSTreeNode* pBSTree);
void convertToDoubleList(BSTreeNode* pCurrent);
 
BSTreeNode *pHead=NULL;//指向循环队列头结点
BSTreeNode *pIndex=NULL;//指向前一个结点

int main()
{
    BSTreeNode *pRoot=NULL;
    addBSTreeNode(pRoot,10);
    addBSTreeNode(pRoot,6);
    addBSTreeNode(pRoot,14);
    addBSTreeNode(pRoot,4);
    addBSTreeNode(pRoot,8);
    addBSTreeNode(pRoot,12);
    addBSTreeNode(pRoot,16);
    inOrderBSTree(pRoot);
	system("pause");
    return 0;
}

//函数参数一定要用引用，这是因为要改变指针的值，否则只改变指针所指向地址的内容
void addBSTreeNode(BSTreeNode *&pCurrent,int value)
{
	if(pCurrent==NULL)
	{
		BSTreeNode *pBSTree = new BSTreeNode();
		pBSTree->m_nValue = value;
		pBSTree->m_pleft = NULL;
		pBSTree->m_pright = NULL;
		pCurrent = pBSTree;
	}
	else if(pCurrent->m_nValue < value)
		addBSTreeNode(pCurrent->m_pright,value);
	else if(pCurrent->m_nValue > value)
		addBSTreeNode(pCurrent->m_pleft,value);
	else
		cout<<"node repeated"<<endl;
}

void inOrderBSTree(BSTreeNode *pBSTree)
{
	if(NULL==pBSTree)
		return; 
	if(NULL != pBSTree->m_pleft)
		inOrderBSTree(pBSTree->m_pleft);
	convertToDoubleList(pBSTree);
	if(NULL != pBSTree->m_pright)
		inOrderBSTree(pBSTree->m_pright);
}

void convertToDoubleList(BSTreeNode *pCurrent)
{
	pCurrent->m_pleft = pIndex;
	if(NULL == pIndex)
		pHead = pCurrent;
	else
		pIndex->m_pright = pCurrent;
	pIndex = pCurrent;
	cout<<pCurrent->m_nValue<<" ";
}