/**

  * Definition for binary tree

  * struct TreeNode {

  *     int val;

  *     TreeNode *left;

  *     TreeNode *right;

  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

  * };

  */

 class Solution {

 public:

    void dfs(vector<int> &ans,TreeNode *root){

         if(!root){

             return;

         }

         dfs(ans,root->left);

         ans.push_back(root->val);

         dfs(ans,root->right);

     }

     vector<int> inorderTraversal(TreeNode *root) {

         vector<int> ans;

         dfs(ans,root);

         return ans;

     }

 };