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class Solution:
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    def validateBinaryTreeNodes(
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        self, n: int, leftChild: List[int], rightChild: List[int]
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    ) -> bool:
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        left_set = set(leftChild)
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        right_set = set(rightChild)
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        que = []
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        for i in range(n):
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            if i not in left_set and i not in right_set:
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                que.append(i)
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        if len(que) > 1 or len(que) == 0:
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            return False
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        graph = defaultdict(list)
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        for i in range(n):
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            graph[i] = []
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            if leftChild[i] != -1:
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                graph[i].append(leftChild[i])
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            if rightChild[i] != -1:
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                graph[i].append(rightChild[i])
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        visited = set()
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        visited.add(que[0])
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        while len(que) > 0:
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            item = que.pop(0)
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            children = graph[item]
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            for child in children:
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                if child not in visited:
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                    que.append(child)
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                    visited.add(child)
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                else:
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                    return False
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        for i in range(n):
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            if i not in visited:
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                return False
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        return True