[1]输入一棵二元查找树，将该二元查找树转换成一个排序的双向链表

/**
* 1：构造二叉查找树；
* 2：中序遍历二叉查找树，因此结点按从小到大顺序访问，
*    假设之前访问过的结点已经调整为一个双向链表，那么
*    只需要将当前结点连接至双向链表的最后一个结点即可，
*    访问完后，双向链表也就调整完了
*
*/
#include <stdio.h>

//      10
//    /   //   6    14
//  / \  /  // 4  8 12  16

struct BSTreeNode
{
    int m_nValue;
    BSTreeNode *m_pLeft;
    BSTreeNode *m_pRight;
};

typedef BSTreeNode DoubleList;  
DoubleList * pHead;  
DoubleList * pListIndex; 
static int i;

/* 建立二叉排序树 */
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
    {
        printf("Node repeated.\n");
    }
}

void Mid_Walk_Tree(BSTreeNode *pRoot)
{
    if(pRoot != NULL)
    {
        if(NULL != pRoot->m_pLeft)
        {
            Mid_Walk_Tree(pRoot->m_pLeft);    
        }
        
        printf("%d ", pRoot->m_nValue);
        
        if(NULL != pRoot->m_pRight)
        {
            Mid_Walk_Tree(pRoot->m_pRight);    
        }
    }
}

void ConvertToDoubleList(BSTreeNode *pCurrent)
{
    pCurrent->m_pLeft = pListIndex;
    if(NULL != pListIndex)
    {
        pListIndex->m_pRight = pCurrent;
    }
    else
    {
        pHead = pCurrent;
    }
    pListIndex = pCurrent;
    printf("pCurrent->m_nValue = %d\n", pCurrent->m_nValue);
}

/* 中序遍历二叉树，同时调整结点指针 */
void inOrderBSTree(BSTreeNode* pBSTree)
{

    if(NULL == pBSTree)
    {
        return;
    }
    
    if(NULL != pBSTree->m_pLeft)
    {
        inOrderBSTree(pBSTree->m_pLeft);
    }
    
    printf("i = %d\n", i);
    
    ConvertToDoubleList(pBSTree);
    
    if(NULL != pBSTree->m_pRight)
    {
        inOrderBSTree(pBSTree->m_pRight);
    }
    i++;
}


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);
    
    //Mid_Walk_Tree(pRoot);
    
    
    inOrderBSTree(pRoot);
    
    
    return 0;
}