Binary Tree Right Side View

/** * 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)     {        vector<int> res;        if (!root)            return res;        queue<TreeNode*> q;        q.push(root);        TreeNode* cur = NULL;        while(!q.empty())        {            int size = q.size();            for(int i = 0; i < size; ++i)            {                cur = q.front();                q.pop();                if (cur->left)                    q.push(cur->left);                if (cur->right)                    q.push(cur->right);            }            res.push_back(cur->val);        }                return res;            }};