Learning On the Way

199. Binary Tree Right Side View

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.

def rightSideView(self, root: TreeNode) -> List[int]: 
    if root is None: 
        return [] 
        
    rightside = [] 
        
    def helper(node: TreeNode, level: int) -> None: 
        if level == len(rightside): 
            rightside.append(node.val) 
        for child in [node.right, node.left]: 
            if child: 
                helper(child, level + 1) 
                
    helper(root, 0) 
    return rightside