leetcode------Binary Tree Right Side View

标题：	Binary Tree Right Side View
通过率：	27.9%
难度：	中等

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].

本题就是个按层次遍历的一种延伸，按层遍历时每次讲每一层的最后一个元素放入结果的list中即可，代码如下：

 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 ArrayList<Integer> rightSideView(TreeNode root) {
12         ArrayList<Integer> res=new ArrayList<Integer>();
13         LinkedList<TreeNode> queue=new LinkedList<TreeNode>();
14         int count=1,tmp=0;
15         if(root==null)return res;
16         queue.addLast(root);
17         while(!queue.isEmpty()){
18             tmp=0;
19             for(int i=1;i<=count;i++){
20                 TreeNode tmptree=queue.removeFirst();
21                 if(i==count)res.add(tmptree.val);
22                 if(tmptree.left!=null){
23                     queue.addLast(tmptree.left);
24                     tmp++;
25                 }
26                 if(tmptree.right!=null){
27                     queue.addLast(tmptree.right);
28                     tmp++;
29                 }
30                 
31             }
32             count=tmp;
33         }
34         return res;
35     }
36 }