二叉搜索树转排序双向链表

二叉搜索树转排序双向链表

示意图：

/*
struct TreeNode {
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int x) :
			val(x), left(NULL), right(NULL) {
	}
};*/
class Solution {
public:
 void ConvertNode(TreeNode* root, TreeNode *& lastnode)  
 {  
    if (root == NULL)  
        return;  
    TreeNode *pCur = root;  
    if (NULL!=pCur->left)  
        ConvertNode(pCur->left, lastnode);  
    pCur->left = lastnode;  
    if (NULL!=lastnode)  
        lastnode->right = pCur;  
    lastnode = pCur;  
    if (NULL!=pCur->right)  
        ConvertNode(pCur->right, lastnode);  
  }  
  TreeNode* Convert(TreeNode* pRootOfTree)
  {   
    TreeNode *lastnode = NULL;  
    ConvertNode(pRootOfTree, lastnode);  
    TreeNode *pCur = lastnode;  
    while (pCur&&pCur->left)  //pCur在排序双链表尾节点处
    {  
        pCur = pCur->left;  
    }  
    return pCur;  
  } 
};