Follow up for problem "Populating Next Right Pointers in Each Node".
What if the given tree could be any binary tree? Would your previous solution still work?
Note:
You may only use constant extra space.

For example,Given the following binary tree,

     1
   /  \
  2    3
 / \    \
4   5    7

After calling your function, the tree should look like:

     1 -> NULL
   /  \
  2 -> 3 -> NULL
 / \    \
4-> 5 -> 7 -> NULL

class Solution {
public:
    void connect(TreeLinkNode *root) {
        while(root!=NULL)
        {
            TreeLinkNode* next = NULL;
            TreeLinkNode* pre = NULL;
            for(;root!=NULL;root=root->next) //遍历的原因是root是一个链表
            {
                if(next==NULL)
                   next = (root->left != NULL) ? root->left : root->right;
                  
                if(root->left)
                {
                    if(pre)
                      pre->next = root->left;
                    pre = root->left;
                }
                
                if(root->right)
                {
                    if(pre)
                      pre->next = root->right;
                    pre = root->right;
                }
                
            }
            root = next;
        }
    }
};