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.

Example:

Input: [1,2,3,null,5,null,4]
Output: [1, 3, 4]
Explanation:

   1            <---
 /   \
2     3         <---
 \     \
  5     4       <---

题目链接：https://leetcode.com/problems/binary-tree-right-side-view/

思路：后来想能不能优化，直接从右子树搜索，发现不行，看个例子

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    
    void fun(queue<TreeNode*>que,vector<int>&res)
    {
        int n=que.size();
        int c=0;
        while(c<n)
        {
            c++;
            TreeNode *tmp=que.front();
            if(c==n)
                res.emplace_back(tmp->val);
            if(tmp->left)
                que.push(tmp->left);
            if(tmp->right)
                que.push(tmp->right);
            que.pop();
        }
        if(que.size()>0)
            fun(que,res);
    }
    vector<int> rightSideView(TreeNode* root) {
        vector<int> res;
        queue<TreeNode*> que;
        if(root==NULL)
            return res;
        que.push(root);
        fun(que,res);
        return res;
    }
};