[grishka]

It almost did for me. I thought that you should be able to divide each number by 2 (or shift one bit) before adding, but that would lose a 1 if both numbers have 1 in their least significant bit. The part with "a & b & 1" fixes that exact issue and is obvious to me in hindsight.

[wildmanx]

> and is obvious to me in hindsight.

Everything is. That's kinda hindsight's thing.

Not so say that a few people in this thread probably saw this solution right away, but the "this was all obvious" crowd in this thread is a little too large for my taste. Be real, guys.

[ygra]

I guess the part about overflow in the title primes most experienced developers to immediately think about a solution where the added numbers are restricted beforehand to avoid the overflow. From there the obvious answer is to halve them, which leaves the next problem when the numbers are odd.

If you're not aware that numbers can overflow (and you probably don't tend to think about that for every single + you type, I guess), then the proper solution is less obvious.