二叉搜索树转化为有序双向链表（C语言）

#include <stdio.h>
#include <stdlib.h>

typedef struct BSTreeNode
{
    int m_nValue;
    BSTreeNode *m_pLeft; 
    BSTreeNode *m_pRight; 
}BSTreeNode;
 
BSTreeNode *pHead=NULL;
BSTreeNode *pIndex=NULL;

void addBSTreeNode(BSTreeNode* &pCurrent,int value)
{
    if (pCurrent==NULL)
    {
        BSTreeNode* pBSTree = NULL;
        pBSTree    = (BSTreeNode*)malloc(sizeof(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);
    }
}

void convertToDoubleList(BSTreeNode* pCurrent)
{
    pCurrent->m_pLeft=pIndex;//使当前结点的左指针指向双向链表中最后一个结点
    if (NULL==pIndex)//若最后一个元素不存在，此时双向链表尚未建立，因此将当前结点设为双向链表头结点
    {
        pHead=pCurrent;
    }
    else//使双向链表中最后一个结点的右指针指向当前结点
    {
        pIndex->m_pRight=pCurrent;
    }
    pIndex=pCurrent;//将当前结点设为双向链表中最后一个结点
    printf("%d ",pCurrent->m_nValue);
}

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);
    }
}

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);
    return 0;
}