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import { TreeNode } from "../binary-tree-inorder-traversal/TreeNode.ts";
export default function isSymmetric(root: TreeNode | null): boolean {    return check(root, root);}const check = (p: TreeNode | null, q: TreeNode | null): boolean => {    if (!p && !q) return true;    if (!p || !q) return false;    return p.val === q.val && check(p.left, q.right) && check(p.right, q.left);};