/*

 struct TreeNode {

     int val;

     struct TreeNode *left;

     struct TreeNode *right;

     TreeNode(int x) :

             val(x), left(NULL), right(NULL) {

     }

 };

 */

 class Solution {

 public:

     TreeNode* KthNode(TreeNode* pRoot, int k)

     {

         if(!pRoot) return nullptr;

         vector<TreeNode*> res;

         Sortnode(pRoot,res);

         if(k<= || k>res.size()) return nullptr;

         return res[k-];

     }

     void Sortnode(TreeNode* root,vector<TreeNode*>& vec){

         if(!root) return;

         Sortnode(root->left,vec);

         vec.push_back(root);

         Sortnode(root->right,vec);

     }

 };