LeetCode. Symmetric Tree [Trees]

Problem:

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree [1,2,2,3,4,4,3] is symmetric:

 

But the following [1,2,2,null,3,null,3] is not:

-Summary-

1. If a tree has no root or root itself exist, it will always return True

2. Otherwise, we keep check below condition recursively of the Tree's left and right subtree 

  - leftSub.left == rightSub.right

  - leftSub.right == rightSub.left

discussion을 보니 아래와 같이 iterative 하게 푸는 방법도 있었다.

 

leetcode.com/problems/symmetric-tree/discuss/33057/Python-iterative-way-using-a-queue

Python iterative way using a queue - LeetCode Discuss

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