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import { TreeNode } from "../mod.ts";
export default function addOneRow(    root: TreeNode | null,    val: number,    depth: number,): TreeNode | null {    if (!root || !depth) return null;
    if (depth === 1) return new TreeNode(val, root);
    if (depth === 2) {        return new TreeNode(            root.val,            new TreeNode(val, root.left),            new TreeNode(val, null, root.right),        );    }
    return new TreeNode(        root.val,        addOneRow(root.left, val, depth - 1),        addOneRow(root.right, val, depth - 1),    );}