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import { TreeNode } from "../binary-tree-inorder-traversal/TreeNode.ts";
export default function tree2str(root: TreeNode | null): string {    if (!root) {        return "";    }    if (!root.left && !root.right) {        return String(root.val);    }    if (!root.right) {        return String(root.val) + "(" + tree2str(root.left) + ")";    }    return (        String(root.val) +        "(" +        tree2str(root.left) +        ")(" +        tree2str(root.right) +        ")"    );}