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].

Java

public class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        List<Integer> rst = new ArrayList<Integer>();
        if(root == null) {
            return rst;
        }

        LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
        queue.add(root);

        while(queue.size() > 0) {
            int size = queue.size();
            for(int i = 0; i < size; i++) {
                TreeNode node = queue.poll();
                if(i == 0) {
                    rst.add(node.val);
                }
                if(node.right != null) {
                    queue.add(node.right);
                }
                if(node.left != null) {
                    queue.add(node.left);
                }
            }
        }

        return rst;
    }
}