How to prove that a problem is NP complete?

Question

I have problem with scheduling. I need to prove that the problem is NP complete. What can be the methods to prove it NP complete?

Answer 1

You need to reduce an NP-Complete problem to the problem you have. If the reduction can be done in polynomial time then you have proven that your problem is NP-complete, if the problem is already in NP, because:

It is not easier than the NP-complete problem, since it can be reduced to it in polynomial time which makes the problem NP-Hard.

See the end of http://www.ics.uci.edu/~eppstein/161/960312.html for more.