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);
}