class Solution

{

public:

    vector<int> inorderTraversal(TreeNode* root)

    {

        vector<int> v;

        inorderTraversalHelp(root, v);

        return v;

    }

    void inorderTraversalHelp(TreeNode *root, vector<int>& v)

    {

        if(root)

        {

            inorderTraversalHelp(root->left, v);

            v.push_back(root->val);

            inorderTraversalHelp(root->right, v);

        }

    }

};