Question

for (long long j = factored_num / 3; j > 2 || factored_num != 1; j -= 2) {

On a 64-bit computer, I’m trying to factor a number. This code works perfectly fine when long long j = factored_num, but when I do integer division, cout << j shows that j is negative — I’m assuming it overflows. How can I fix this?

I’ve tried 3LL, j-= 2LL, etc. in case it was a type problem. Again, it definitely has to do with the division part, but I’m not familiar enough with data types to immediately get the problem.

Answer 1

The problem could be the final condition. You loop while j is more than 2 or factored_num is not 1, so if factored_num does not become one, the loop will not end and j will continue to decrement to negative numbers.

I’d expect the condition to be j > 2 && factored_num != 1, that is you want to end if j is 2 or less (why 2; 2 is a valid factor) or factored_num is 1 (and therefore does not have any more factors).