Mapping two integers to one, in a unique and deterministic way

Question

Imagine two positive integers A and B. I want to combine these two into a single integer C.

There can be no other integers D and E which combine to C. So combining

Answer 1

Check this: http://en.wikipedia.org/wiki/Pigeonhole_principle. If A, B and C are of same type, it cannot be done. If A and B are 16-bit integers, and C is 32-bit, then you can simply use shifting.

The very nature of hashing algorithms is that they cannot provide a unique hash for each different input.