difference between np complete and np hard
could anybody tell me the difference between np hard and np complete (in simple way). I have read articles on many sites but they are a bit complex.
now this is what I think
np complete problems are those problems whose solution can be verified in polynomial time by a non deterministic turing machine.
np hard problems are the hardest problems whose solution might not be verifiable.
please do correct me if i am wrong.
also a problem is np hard if there exist np complete problem that is reducible to np harp problem