Populating Next Right Pointers in Each Node II

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

问题描述：给定一个二叉树，使每个节点的next指针指向它的右边的节点，和之前的Populating Next Right Pointers in Each Node类似，只是这次的二叉树不是完全二叉树，但是方法和思想与之前的一样。