算法——二叉搜索树转换成双向链表c++实现_将二叉搜索树转换为双向排序链表c++

题目：将二叉搜索树换成双向链表

思路：利用树的中序遍历（左根右），再利用两个“快慢”指针，pLast比pCur慢一步，通过这两个指针建立双向链表

BinaryTreeNode* Convert(BinaryTreeNode* pRootOfTree)
{
    BinaryTreeNode *pLastNodeInList = nullptr;
    ConvertNode(pRootOfTree, &pLastNodeInList);
 
    // pLastNodeInList指向双向链表的尾结点，
    // 我们需要返回头结点
    BinaryTreeNode *pHeadOfList = pLastNodeInList;
    while(pHeadOfList != nullptr && pHeadOfList->m_pLeft != nullptr)
        pHeadOfList = pHeadOfList->m_pLeft;
 
    return pHeadOfList;
}
 
void ConvertNode(BinaryTreeNode* pNode, BinaryTreeNode** pLastNodeInList)
{
    if(pNode == nullptr)
        return;
 
    BinaryTreeNode *pCurrent = pNode;
 
    if (pCurrent->m_pLeft != nullptr)
        ConvertNode(pCurrent->m_pLeft, pLastNodeInList);
 
    pCurrent->m_pLeft = *pLastNodeInList; 
    if(*pLastNodeInList != nullptr)
        (*pLastNodeInList)->m_pRight = pCurrent;
 
    *pLastNodeInList = pCurrent;
    if (pCurrent->m_pRight != nullptr)
        ConvertNode(pCurrent->m_pRight, pLastNodeInList);
}