Symmetric Tree

Easy

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

Example 1

Input:  root = [1,2,2,3,4,4,3]
Output: true

Example 2

Input:  root = [1,2,2,null,3,null,3]
Output: false

Constraints

• 1 <= number of nodes <= 1000
• -100 <= Node.val <= 100