Some professors would provide past exams for study aids or use them as homework problems.
However, the explicit default was that you should not look at solutions from prior years. Professors would announce at the beginning of the course that they reuse questions and looking at prior years solutions was an honor code violation. I think it's pretty clear it's cheating when the expectations are clearly outlined.
If you had inadvertently come across the problem before and independently solved it, you were expected to disclose that as part of your answer. I personally had to do this several times, and never suffered any negative consequences for it, but the expectation for honesty was there.
However, the explicit default was that you should not look at solutions from prior years. Professors would announce at the beginning of the course that they reuse questions and looking at prior years solutions was an honor code violation. I think it's pretty clear it's cheating when the expectations are clearly outlined.
If you had inadvertently come across the problem before and independently solved it, you were expected to disclose that as part of your answer. I personally had to do this several times, and never suffered any negative consequences for it, but the expectation for honesty was there.