声明：取自 ”july“的“微软100题“，加上一些个人理解，欢迎拍砖。
原文地址：http://blog.csdn.net/v_july_v/article/details/6126406
学习微软100题笔记：
1.二元查找树变双向链表：
#include <stdio.h>
#include <iostream>
struct BSTreeNode
{
int m_nValue;
BSTreeNode *m_pLeft;
BSTreeNode *m_pRight;
};
typedef BSTreeNode DoubleList;
DoubleList * pHead;
DoubleList * pListIndex;
void convertToDoubleList(BSTreeNode * pCurrent);
BSTreeNode* addBSTreeNode(BSTreeNode * & pCurrent, int value)
{
if (NULL == pCurrent)
{
pCurrent = new BSTreeNode();
pCurrent->m_pLeft = NULL;
pCurrent->m_pRight = NULL;
pCurrent->m_nValue = value;
}
else if( pCurrent->m_nValue > value )
{
pCurrent->m_pLeft = addBSTreeNode( pCurrent->m_pLeft, value );
}
else if ( pCurrent->m_nValue< value )
{
pCurrent->m_pRight = addBSTreeNode(pCurrent->m_pRight, value);
}
else
{
std::cout<<"重复加入节点"<< std::endl;
}
return pCurrent;
}
void ergodicBSTree( BSTreeNode *pCurrent )
{
if( NULL == pCurrent )
{
return;
}
if( NULL != pCurrent->m_pLeft )
{
ergodicBSTree( pCurrent->m_pLeft );
}
convertToDoubleList( pCurrent );
if( NULL != pCurrent->m_pRight )
{
ergodicBSTree( pCurrent->m_pRight );
}
}
void convertToDoubleList( BSTreeNode *pCurrent )
{
pCurrent->m_pLeft = pListIndex;
if( NULL != pListIndex )
{
pListIndex->m_pRight = pCurrent;
}
else
{
pHead = pCurrent;
}
pListIndex = pCurrent;
std::cout << pCurrent->m_nValue << std::endl;
}
int
main( void )
{
BSTreeNode *pRoot = NULL;
pListIndex = NULL;
pHead = NULL;
addBSTreeNode(pRoot, 10);
addBSTreeNode(pRoot, 4);
addBSTreeNode(pRoot, 6);
addBSTreeNode(pRoot, 8);
addBSTreeNode(pRoot, 12);
addBSTreeNode(pRoot, 14);
addBSTreeNode(pRoot, 15);
addBSTreeNode(pRoot, 16);
ergodicBSTree(pRoot);
return 0;
}
其中建立二叉树时是按照 c语言程序设计中（K&R）方法建立的，大同小异。
重点是利用递归转换为链表的过程。
一个全局指针pListIndex指向pCurrent的前一个节点，每次调用convertToDoubleList完成
pCurrent->m_pRight -> pListIndex;因为这里pCurrent不为NULL，然后再pListIndex->m_pLift 指向当前pCurrent
要先判断pListIndex是否为NULL，因为pListIndex开始时是赋值为NULL的,不能进行解引用操作。
新手没经验，欢迎指正错误，待更新。详细请见开头原博文 ，july大神。