You should file a non-resident return for NC. If you went to NC to work during the summer and then you returned back home to AL - your trip would be considered temporary. You were not a resident of NC so you don't have to do part-year returns. Short term stays that you intend to return home from are not permanent moves. The temporary residency can be for school, work, medical reasons, incarceration, etc....
Do I have to file tax returns in more than one state?
Why would I have to file a nonresident state return?
How do I file a nonresident state return? - - Follow these instructions - do not indicate that you moved and check the box that says I have Other State Income.