199. Binary Tree Right Side View

solution.py

from collections import deque
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def append_or_overwrite(self, node: TreeNode, depth: int, seen: List[int]):
        if len(seen) == depth:
            seen.append(node.val)
        seen[depth] = node.val

    def rightSideView(self, root: Optional[TreeNode]) -> List[int]:
        if root is None:
            return list()
        queue = deque([(0, root)])
        seen = [root.val]
        while len(queue) > 0:
            depth, curr_node = queue.popleft()
            if curr_node is None:
                continue
            next_depth = depth + 1
            queue.append((next_depth, curr_node.left))
            queue.append((next_depth, curr_node.right))
            if curr_node.left is not None:
                self.append_or_overwrite(curr_node.left, next_depth, seen)
            if curr_node.right is not None:
                self.append_or_overwrite(curr_node.right, next_depth, seen)
        return seen