[sbrother]

That is mind blowing, but it’s not immediately obvious to me that it’s equivalent for n > sqrt(INT_MAX). Is it? And if so, is the compiler somehow smart enough to know that?

[marin049]

Integer overflow is actually undefined behaviour thus the compiler is free to assume it doesn't happen.

[xigoi]

If you assume two’s complement arithmetic, then this is always equivalent because you’re basically just calculating the answer in a modular ring.