Duplicate Detection in an arbitrary set

[Tyler Earman]

Does anyone know of a semi-efficient way of detecting duplicates in a
given set of data (specifically duplicate integers) other than just
sorting the data into an array and then stepping through each element in
the array?

Preferably a solution wouldn't involve something implementation specific
(like loading the array into a different data type and measuring the
differences between the two, saw someone doing that with Java ArrayLists
and HashSets) but rather some sort of mathematically correct method of
doing it.

Thanks for the help.

-Tyler Earman