private static void Helper(LeetCode285TreeNode root)
{
if (root == null)
{
return;
}
Helper(root.left);
list.Add(root);
Helper(root.right);
}
public static LeetCode285TreeNode InorderSuccessor(LeetCode285TreeNode root, LeetCode285TreeNode p)
{
if (root == null || p == null)
{
return(null);
}
Helper(root);
var index = list.FindIndex(x => x.val == p.val);
return(index >= 0 && (index + 1 < list.Count) ? list[index + 1] : null);
}