### treeDiameter 
from collections import defaultdict
from typing import *
def f_gold(edges: List[List[int]]) -> int:
    def dfs(u, t):
        nonlocal ans, vis, d, next
        if vis[u]:
            return
        vis[u] = True
        for v in d[u]:
            dfs(v, t + 1)
        if ans < t:
            ans = t
            next = u
    d = defaultdict(set)
    vis = [False] * (len(edges) + 1)
    for u, v in edges:
        d[u].add(v)
        d[v].add(u)
    ans = 0
    next = 0
    dfs(edges[0][0], 0)
    vis = [False] * (len(edges) + 1)
    dfs(next, 0)
    return ans