static void Main(string[] args)
{
Solution s = new Solution();
var res = s.InOrderSuccessor(TestSolution.DesignBT4(), 7);
System.Console.WriteLine(res?.val);
}
static void Main(string[] args)
{
Solution s = new Solution();
var res = s.BTtoArray(TestSolution.DesignBT1());
for (int i = 0; i < res.Length; i++)
{
if (res[i] == 0)
{
System.Console.Write("null" + " ");
}
else
{
System.Console.Write(res[i] + " ");
}
}
}