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].

Top view, Bot view, right view, and left view.

1 /** 2  * Definition for binary tree 3  * public class TreeNode { 4  *     int val; 5  *     TreeNode left; 6  *     TreeNode right; 7  *     TreeNode(int x) { val = x; } 8  * } 9  */10 public class Solution {11     public List
     
       rightSideView(TreeNode root) {12         List
      
        result = new ArrayList
       
        ();13         if(root == null) return result;14         LinkedList
        
          queue = new LinkedList
         
          ();15         queue.add(root);16         queue.add(null);17         int level = 0;18         while(queue.size() != 1){19             TreeNode tmp = queue.poll();20             if(tmp == null){21                 queue.add(null);22                 level ++;23             }else{24                 if(result.size() == level){25                     result.add(tmp.val);26                 }else{27                     result.set(level,tmp.val);28                 }29                 if(tmp.left != null)queue.add(tmp.left);30                 if(tmp.right != null)queue.add(tmp.right);31             }32         }33         return result;34     } 35 }