/**

  * Definition for a binary tree node.

  * public class TreeNode {

  *     int val;

  *     TreeNode left;

  *     TreeNode right;

  *     TreeNode(int x) { val = x; }

  * }

  */

 public class Solution {

     public int kthSmallest(TreeNode root, int k) {

         List<Integer> list=new ArrayList<>();

         list=midTree(root);

         return list.get(k-1);

     }

     public List<Integer> midTree(TreeNode root){

         List<Integer> list=new ArrayList<>();

          if(root.left!=null)

              list.addAll(midTree(root.left));

          list.add(root.val);

          if(root.right!=null)

               list.addAll(midTree(root.right));

          return list;

     }

 }