Binary Tree Right Side View LeetCode solution in Python

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# Runtime: 54 ms (Top 45.43%) | Memory: 13.9 MB (Top 70.59%)
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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    def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
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        def dfs(root, d):
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            if not root:
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                return
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            if self.maxi < d:
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                self.res.append(root.val)
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                self.maxi = d
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            dfs(root.right, d + 1)
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            dfs(root.left, d + 1)
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        self.res, self.maxi = [], 0
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        dfs(root, 1)
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        return self.res
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        # An Upvote will be encouraging