Symmetric Tree
Given a binary tree, return true if it is symmetric around its center.
Examples
Input: [1,2,2,3,4,4,3]
Output: true
Input: [1,2,2,null,3,null,3]
Output: false
Hints
Implement a helper function that takes two tree nodes and checks if they are mirror images of each other (same value, left child of one matches right child of the other, and vice versa).
Handle edge cases where one subtree is null while the other isn't by returning false immediately.
Optimize the solution to avoid redundant checks by comparing nodes level by level (BFS) instead of recursively traversing the entire tree.
Related Problems
Symmetric Tree
Given a binary tree, return true if it is symmetric around its center.