123456789101112131415161718
import { TreeNode } from "../binary-tree-inorder-traversal/TreeNode.ts";
export default function kthSmallest(root: TreeNode | null, k: number): number {    const res: number[] = [];    // 中序遍历    const inOrder = (root: TreeNode | null) => {        if (!root) return;        inOrder(root.left);        res.push(root.val);        if (typeof res[k - 1] === "number") {            return;        }        inOrder(root.right);    };    inOrder(root);    return res[k - 1];}