# Problem Definition

## Description

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

Example:

```plaintext
    1
   / \
  2   2
 / \ / \
3  4 4  3
```

The above binary tree is symmetric.

But the following is not:

```plaintext
    1
   / \
  2   2
   \   \
   3    3
```

Return `0 / 1` (0 for false, 1 for true) for this problem.

## Notes

1. [Geeks for Geeks post](https://www.geeksforgeeks.org/symmetric-tree-tree-which-is-mirror-image-of-itself/)
1. [LeetCode discussion - 1ms recursive Java Solution, easy to understand](https://leetcode.com/problems/symmetric-tree/discuss/33104/1ms-recursive-Java-Solution-easy-to-understand)
1. [LeetCode discussion - Recursive and non-recursive solutions in Java](https://leetcode.com/problems/symmetric-tree/discuss/33054/Recursive-and-non-recursive-solutions-in-Java)