Envío 5181

Código

N = int(input())
g = [[] for _ in range(N)]
time_in  = [None for _ in range(N)]
time_out = [None for _ in range(N)]

for _ in range(N - 1):
    p, n = map(int, input().split())    
    g[p].append(n)

def dfs(node):
    s = [[node, 0]]
    time = time_in[node] = 0
    while s:
        node, i = s[-1]

        # if it still
        # has children
        # then add them
        if i < len(g[node]): 
            s[-1][1] += 1
            s.append([g[node][i], 0])
            time_in[g[node][i]] = time + 1
        else: 
            s.pop()
            time_out[node] = time
        time += 1

def query(a, b):
    return time_in[a] <= time_in[b] <= time_out[a]

dfs(0)

Q = int(input())
for _ in range(Q):
    a, b = map(int, input().split(" "))
    print("Yes" if query(a, b) else "No")