leetcode-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]

.

/**
* 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:
vector<int> rightSideView(TreeNode* root) {
if(!root)
return vector<int>();
deque<TreeNode*>  que;
vector<int> res;
que.push_back(root);

while(!que.empty()){
res.push_back(que.back()->val);
int size=que.size();
while(size--){
TreeNode *temp=que.front();
que.pop_front();
if(temp->left)
que.push_back(temp->left);
if(temp->right)
que.push_back(temp->right);
}

}
return res;
}
};