199. 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) {        std::vector<int> v;        if(!root) return v;        queue<TreeNode*> q;        q.push(root);        while(!q.empty()){            int size_q=q.size();            TreeNode* tmp;            for(int i=0;i<size_q;i++){                tmp=q.top();                q.pop();                if(tmp->left) q.push(tmp->left);                if(tmp->right) q.push(tmp->right);            }            v.push_back(tmp->val);        }        return v;    }};