Binary Tree Right Side View

Given a binary tree, imagine yourself standing on the rightside 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].

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List<Integer> rightSideView(TreeNode root) 
    {
        List<Integer> res = new ArrayList<Integer>();
        Queue<TreeNode> queue = new LinkedList<TreeNode>();
        if(root==null) return res;
        queue.add(root);
        while(!queue.isEmpty())
        {
            int levelnum = queue.size();
            List<Integer> sublist = new ArrayList<Integer>();
            for(int i=0; i<levelnum;i++)
            {
                TreeNode node = queue.poll();
                if(node.left!=null) queue.add(node.left);
                if(node.right!=null) queue.add(node.right);
                sublist.add(node.val);
            }
            int size = sublist.size();
            res.add(sublist.get(size-1));
        }
        return res;      
    }
}

very similar with Binary Tree Level Order Traverse

http://www.cnblogs.com/hygeia/p/4704027.html