Populating Next Right Pointers in Each Node II

標籤：leetcode   遍曆   traversal   

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

使用一個隊列儲存當前節點和當前層號，prev儲存這個節點的前一個節點，如果節點屬於同一層，則prev的next指向隊列的頭元素。

層次遍曆