题目
Given 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.
解题思路
使用字典存每一行的最右边元素，使用dfs遍历左右子树同时维护结点的深度，每次出现新的深度，该节点为最右边节点
代码
class Solution:
def rightSideView(self, root: TreeNode) -> List[int]:
if not root:
return []
res, max_depth = {}, 0
stack = [(root, 0)]
while stack:
cur, depth = stack.pop()
max_depth = max(max_depth, depth)
res.setdefault(depth, cur.val)
if cur.left:
stack.append((cur.left, depth + 1))
if cur.right:
stack.append((cur.right, depth + 1))
return [res[depth] for depth in range(max_depth + 1)]
