Binary Tree Right Side View.java

/*
    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.
    
    Link: https://leetcode.com/problems/binary-tree-right-side-view/

    Example: For example:
		Given the following binary tree,
		   1            <---
		 /   \
		2     3         <---
		 \     \
		  5     4       <---
		You should return [1, 3, 4].

    Solution: None
    
    Source: None
*/

/**
 * 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> view = new ArrayList<Integer>();
        if (null == root) {
        	return view;
        }
        dfs(view, root, 1);
        return view;
    }
    private void dfs(List<Integer> view, TreeNode root, int layer){
        if (root == null) {
        	return;
        }
        if (layer > view.size()) {
        	view.add(root.val);
        } 
        dfs(view, root.right, layer + 1);
        dfs(view, root.left, layer + 1);
    }
}