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Java-based LeetCode algorithm problem solutions, regularly updated
101\. Symmetric Tree
Easy
Given the `root` of a binary tree, _check whether it is a mirror of itself_ (i.e., symmetric around its center).
**Example 1:**
![](https://assets.leetcode.com/uploads/2021/02/19/symtree1.jpg)
**Input:** root = [1,2,2,3,4,4,3]
**Output:** true
**Example 2:**
![](https://assets.leetcode.com/uploads/2021/02/19/symtree2.jpg)
**Input:** root = [1,2,2,null,3,null,3]
**Output:** false
**Constraints:**
* The number of nodes in the tree is in the range `[1, 1000]`.
* `-100 <= Node.val <= 100`
**Follow up:** Could you solve it both recursively and iteratively?