Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).
For example:
Given binary tree {3,9,20,#,#,15,7},
return its bottom-up level order traversal as:
解法一:
<a>// Iterative</a>
下面我们来看递归的解法,核心就在于我们需要一个二维数组,和一个变量level,当level递归到上一层的个数,我们新建一个空层,继续往里面加数字,参见代码如下:
解法二:
<a>// Recurive</a>
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