20180211GetNext

/*
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==nullptr)
            return nullptr;
        if(pNode->right!=nullptr){
            TreeLinkNode* p=pNode->right;
            while(p->left!=nullptr){
                p=p->left;
            }
                
            return p;
        }
        if(pNode->next!=nullptr){
            if(pNode==pNode->next->left)
                return pNode->next;
            if(pNode==pNode->next->right){
                TreeLinkNode* p=pNode->next;
                while(p->next!=nullptr&&p==p->next->right){
                    p=p->next;
                }
                return p->next;
            }
        }
        return nullptr;
    }
};