binary_tree_right_side_view.py

'''
Given the root of a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
'''


class Solution:
    def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
        if not root:
            return []
        q = deque([root])
        ans = []
        while q:
            length = len(q)
            ans.append(q[-1].val)
            for _ in range(length):
                node = q.popleft()
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
        return ans