Binary Tree Right Side View

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代码：

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List<Integer> rightSideView(TreeNode root) {
        List result = new ArrayList();
        if(null == root)
            return result;
        List result_left = rightSideView(root.left);
        List result_right = rightSideView(root.right);
        result.add(root.val);
        result.addAll(result_right);
        if(result_left.size() > result_right.size()){
            result.addAll(result_left.subList(result_right.size()-1,result_left.size-1));
        }
        return result;
    }
}