/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public int kthSmallest(TreeNode root, int k) {
if(root==null){
return 0;
}
List<Integer> result = new ArrayList<>();
midTraverse(root,result);
return result.get(k-1);
}
public void midTraverse(TreeNode node,List<Integer> result){
if(node==null){
return;
}
midTraverse(node.left,result);
result.add(node.val);
midTraverse(node.right,result);
}
}