Leetcode 199. Binary Tree Right Side view (two-pronged)

Original title URL: https://leetcode.com/problems/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].

Method: Depth First.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode (int x) {val = x;}
 * *
/public class solution {
    private void rightmost (TreeNode root, int depth, list<integer> List) {
        if (depth = = List.size ()) List.add (root.val);
        if (root.right! = null) rightmost (root.right, depth + 1, list);
        if (root.left! = null) rightmost (root.left, depth + 1, list);
    }
    Public list<integer> Rightsideview (TreeNode root) {
        list<integer> List = new arraylist<> ();
        if (root = null) return list;
        Rightmost (root, 0, list);
        return list;
    }
}