1234567891011121314151617181920212223242526
import { TreeNode } from "../mod.ts";export default function longestUnivaluePath(root: TreeNode | null): number {    if (!root) return 0;
    let res = 0;
    dfs(root, (s) => res = Math.max(res, s));    return res;}function dfs(root: TreeNode | null, out: (s: number) => void) {    if (!root) {        return 0;    }    const left = dfs(root.left, out);    const right = dfs(root.right, out);    let left1 = 0, right1 = 0;    if (root.left && root.left.val === root.val) {        left1 = left + 1;    }    if (root.right && root.right.val === root.val) {        right1 = right + 1;    }    out(left1 + right1);    return Math.max(left1, right1);}