二叉树的下一个节点

/*
struct TreeLinkNode {
int val;
struct TreeLinkNode *left;
struct TreeLinkNode *right;
struct TreeLinkNode *next;
TreeLinkNode(int x) :val(x), left(NULL), right(NULL), next(NULL) {

}
};
*/
//next是指父节点
class Solution {
public:
TreeLinkNode* GetNext(TreeLinkNode* pNode)
{
if(pNode==NULL)
return NULL;
if(pNode->right!=NULL)
{
pNode = pNode->right;
while(pNode->left!=NULL)
{
pNode = pNode->left;
}
return pNode;
}
else if(pNode->right==NULL)
{
struct TreeLinkNode* pParent = pNode->next;
struct TreeLinkNode* pCurrent = pNode;
while(pParent!=NULL&&pCurrent==pParent->right)
{
pCurrent=pParent;
pParent=pParent->next;
}
return pParent;
}
return NULL;
}
};