Symmetric Tree

1class Solution {
2    public boolean isSymmetric(TreeNode root) {
3        // An empty tree is symmetric
4        if (root == null) return true;
5        // Use a helper function to compare left and right subtree
6        return isMirror(root.left, root.right);
7    }
8
9    private boolean isMirror(TreeNode t1, TreeNode t2) {
10        // If both nodes are null, they are mirrors
11        if (t1 == null && t2 == null) return true;
12        // If one node is null, not mirrors
13        if (t1 == null || t2 == null) return false;
14        // Check values and recurse on children, swapping roles
15        return (t1.val == t2.val) &&
16               isMirror(t1.right, t2.left) &&
17               isMirror(t1.left, t2.right);
18    }
19}