public void appendToTail(int d)
{
Node end = new Node(d);
Node n = this;
while (n.next != null)
{
n = n.next;
}
n.next = end;
}
public void push(int d)
{
Node item = new Node(d);
item.next = top;
top = item;
}
public int? pop()
{
if (top != null)
{
Node item = top;
top = top.next;
return item.data;
}
return null;
}