剑指offer No.57 二叉树的下一个结点

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

        } 

        while(pNode->next!=NULL)

        {

            TreeLinkNode *proot=pNode->next;

            if(proot->left==pNode)

                return proot;

            pNode=pNode->next;

        }

        return NULL;

    }

};