class Solution:
    def largestValues(self, root: Optional[TreeNode]) -> List[int]:
        if root is None:
            return []
        ans = []
        q = [root]
        while q:
            maxVal = -inf
            tmp = q
            q = []
            for node in tmp:
                maxVal = max(maxVal, node.val)
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
            ans.append(maxVal)
        return ans