[Leetcode]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

Populating Next Right Pointers in Each Node的扩展题~还是要求用常数空间，不过树不是完全二叉树~下面解法其实思路挺简单的，明白了的话写起来也会很顺手~

class Solution:    # @param root, a tree node    # @return nothing    def connect(self, root):        cur, head, prev = root, None, None        while cur:            while cur:                if cur.left:                    if prev:                        prev.next = cur.left                    else:                        head = cur.left                    prev = cur.left                if cur.right:                    if prev:                        prev.next = cur.right                    else:                        head = cur.right                    prev = cur.right                cur = cur.next            cur = head            prev, head = None, None