### validateBinaryTreeNodes 
from typing import *
def f_gold(n: int, leftChild: List[int], rightChild: List[int]
) -> bool:
    p = list(range(n))
    vis = [False] * n
    def find(x):
        if p[x] != x:
            p[x] = find(p[x])
        return p[x]
    for i in range(n):
        l, r = leftChild[i], rightChild[i]
        if l != -1:
            if vis[l] or find(i) == find(l):
                return False
            p[find(i)] = find(l)
            vis[l] = True
            n -= 1
        if r != -1:
            if vis[r] or find(i) == find(r):
                return False
            p[find(i)] = find(r)
            vis[r] = True
            n -= 1
    return n == 1