中序遍历

void ConvertNode(BSTreeNode* pNode, BSTreeNode*& pLastNodeInList)
{
if(pNode == NULL)
return;

BSTreeNode *pCurrent = pNode;

// Convert the left sub-tree
if (pCurrent->m_pLeft != NULL)
ConvertNode(pCurrent->m_pLeft, pLastNodeInList);

// Put the current node into the double-linked list
pCurrent->m_pLeft = pLastNodeInList;
if(pLastNodeInList != NULL)
pLastNodeInList->m_pRight = pCurrent;

pLastNodeInList = pCurrent;

// Convert the right sub-tree
if (pCurrent->m_pRight != NULL)
ConvertNode(pCurrent->m_pRight, pLastNodeInList);
}

///////////////////////////////////////////////////////////////////////
// Covert a binary search tree into a sorted double-linked list
// Input: pHeadOfTree - the head of tree
// Output: the head of sorted double-linked list
///////////////////////////////////////////////////////////////////////
BSTreeNode* Convert_Solution1(BSTreeNode* pHeadOfTree)
{
BSTreeNode *pLastNodeInList = NULL;
ConvertNode(pHeadOfTree, pLastNodeInList);

// Get the head of the double-linked list
BSTreeNode *pHeadOfList = pLastNodeInList;
while(pHeadOfList && pHeadOfList->m_pLeft)
pHeadOfList = pHeadOfList->m_pLeft;

return pHeadOfList;
}

把二元查找树转变成排序的双向链表