# https://leetcode.com/problems/binary-tree-right-side-view

from collections import deque
from typing import Deque, List, Optional, Set, Tuple

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class Solution:
    def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
        result: List[int] = []
        q: Deque[Tuple[TreeNode, int]] = deque()
        levels: Set[int] = set()

        if root is None:
            return result

        q.append((root, 0))
        while len(q) > 0:
            (curr, curr_level) = q.popleft()
            if curr_level not in levels:
                levels.add(curr_level)
                result.append(curr.val)
            if curr.right is not None:
                q.append((curr.right, curr_level + 1))
            if curr.left is not None:
                q.append((curr.left, curr_level + 1))

        return result