199. Binary Tree Right Side View

• categories: Code, Interview Question, leetcode, Medium
• source: https://leetcode.com/problems/binary-tree-right-side-view
• topics: Tree

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.

DFS

# 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 rightSideView(self, root: Optional[TreeNode]) -> List[int]:
        ans = {}
        if not root:
            return []
 
        def dfs(node, depth):
            nonlocal ans
            if not depth in ans:
                ans[depth] = node.val
            if node.right:
                dfs(node.right, depth + 1)
            if node.left:
                dfs(node.left, depth + 1)
 
        dfs(root, 0)
 
        return list(ans.values())