"Direct addressing is a simple technique that works well when the universe U of
keys is reasonably small. Suppose that an application needs a dynamic set in which
each element has a key drawn from a not too large universe U. We shall assume that no two elements have the same key.
To represent the dynamic set, we use an array, or direct-address table, denoted
by T =[0, ...m-1]. Why can't the size of the universe be very large?"
The Attempt at a Solution
I am entertaining the possibility that storing a large set of keys might be heavy on memory. However, I am not quite convinced: If we know that we are going to need a lot of keys for an application, then storing a large array is going to be resource-draining anyway.