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.

For example:

Given the following binary tree,

1            <---
 /   \
2     3         <---
 \     \
  5     4       <---

You should return

[1, 3, 4]

.

public class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        List<Integer> result = new ArrayList<Integer>();
        helper(root,result,0);
        return result;
    }
    
    public void helper(TreeNode node, List<Integer> result, int count){
        if(node == null){
            return;
        }
        if(count == result.size()){
            result.add(node.val);
        }
        helper(node.right,result,count + 1);
        helper(node.left,result,count + 1);
    }
}