public void Add(string code, int depart_time, int arrival_time)
{
if (root == null)
{
Node newnode = new Node(code, depart_time, arrival_time);
root = newnode;
keys.Add(depart_time);
members++;
}
else if (!keys.Contains(depart_time))
{
root.insertData(ref root, code, depart_time, arrival_time);
keys.Add(depart_time);
members++;
}
}