private static void Helper(LeetCode230TreeNode root)
{
if (root == null)
{
return;
}
Helper(root.left);
list.Add(root.val);
Helper(root.right);
}
public static int KthSmallestElement(LeetCode230TreeNode root, int k)
{
Helper(root);
return(list[k - 1]);
}
public LeetCode230TreeNode(int val = 0, LeetCode230TreeNode left = null, LeetCode230TreeNode right = null)
{
this.val = val;
this.left = left;
this.right = right;
}