Binary Tree Right Side View

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
     vector<int> v;
    vector<int> rightSideView(TreeNode* root) {
        if(root==NULL)
        {
            return v;
        }
        recursion(root,0);
        return v;
    }
    void recursion(TreeNode* root,int level)
    {
           if(root==NULL)
           {
            return;
           }
           if(level==v.size())
           {
            v.push_back(root->val);
           }
           recursion(root->right,level+1);
           recursion(root->left,level+1);
    }
};