from collections import deque

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

def rightSideView(root):
    result = []
    if not root:
        return result

    q = deque([root])

    while q:
        sz = len(q)
        for i in range(sz):
            node = q.popleft()

            __________________________

            if node.left:
                q.append(node.left)
            if node.right:
                q.append(node.right)

    return result