Binary Tree Inorder Traversal

/**
* 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> inorderTraversal(TreeNode* root) {
vector<int> res;
inorderVisit(root,res);
return res;

}
void inorderVisit(TreeNode * temp,vector<int>& res)
{
if(temp==NULL)
return;
if(temp->left!=NULL)
inorderVisit(temp->left,res);
res.push_back(temp->val);
if(temp->right!=NULL)
inorderVisit(temp->right,res);
}
};