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class Solution:
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    def isSameTree(self, p: Optional[TreeNode], q: Optional[TreeNode]) -> bool:
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        stack = [[p, q]]
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        while stack:
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            p, q = stack.pop()
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            if not p and not q:  # (1)
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                continue
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            elif p and q and p.val == q.val:  # (2)
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                stack.append([p.left, q.left])
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                stack.append([p.right, q.right])
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            else:  # (3)
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                return False
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        return True