【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].

 

class Solution {
public:
    vector<int> rightSideView(TreeNode* root) {
        vector<int> ret;
        if(root==NULL) return ret;

        queue<TreeNode*> Q;
        Q.push(root);
        TreeNode * node;
        while(!Q.empty()){
            int qlen=Q.size();
            for(int i=0;i<qlen;i++){
                node=Q.front();
                Q.pop();

                if(node->left) Q.push(node->left);
                if(node->right) Q.push(node->right);

            }
            ret.push_back(node->val);
        }

        return ret;
    }
};