199. Binary Tree Right Side View.py

"""
    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.
    
    Example:
    
    Input: [1,2,3,null,5,null,4]
    Output: [1, 3, 4]
    Explanation:
    
      1           <---
     / \
    2   3         <---
     \   \
      5   4       <---

"""
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None


def rightSideView(root):
    """
    :type root: TreeNode
    :rtype: List[int]
    """
    self.res = []
    def dfs(node,depth):
    if not node:
        return
    if depth == len(self.res):  #will add the right val first in every level
        self.res.append(node.val)
            
        dfs(node.right, depth+1)
        dfs(node.left, depth+1)

dfs(root,0)
return self.res