Late Policy: If you hand in something after the due date without the explicit approval of the instructor or the TA, you might receive zero credit. Homeworks are due at the beginning of class on the assigned due date. Under real emergencies, extensions might be given by the instructor if you contact the instructor in advance.
Cooperation on Homework and Exams: Collaboration on homework or projects, or sharing or copying of solutions, is not allowed. Of course, no cooperation is allowed on exams. The department academic honesty policy is listed in: http://www.cs.columbia.edu/education/honesty. It is your responsibility to be aware of this policy, and to conform to it.