Populate pointers to each node II@leetcode

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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

» Solve this problem
直接用问题1的code也可以通过test cases，bfs遍历就可以了，拿q来存每一层的node，比下面的code耗的space要多。