Arrays of distinct representatives — a very simple NP-complete problem

A Simplified NP-Complete MAXSAT Problem

It is shown that the MAX2SAT problem is NP-complete even if every variable appears in at most three clauses. However, if every variable appears in at most two clauses, it is shown that it (and even the general MAXSAT problem) can be solved in linear time. When every variable appears in at most three clauses, we give an exact algorithm for MAXSAT that takes at most O(3 n=2 n) steps where n is th...

A simplified NP-complete satisfiability problem

Cook [l] has shown that 3-SAT, the Boolean satisfiability problem restricted to instances with exactly three variables per clause, is NP-complete. This is a tightest possible restriction on the number of variables in a clause because as Even et al. [2] demonstrate, 2-SAT is in P. Horowitz and Sahni [5] point up the importance of finding the strongest possible restrictions under which a problem ...

The Minimal Logically-Defined NP-Complete Problem

An Average Case NP-complete Graph Problem

NP-complete problems should be hard on some instances but these may be extremely rare. On generic instances many such problems, especially related to random graphs, have been proven easy. We show the intractability of random instances of a graph coloring problem: this graph problem is hard on average unless all NP problem under any samplable (i.e. generateable in polynomial time) distribution a...

System Design Is an NP-Complete Problem

The system design process translates the customers’ needs into a buildable system design. It requires selecting subsystems from an allowable set and matching the interfaces between them. Designs that meet the top-level input and output requirements are tested to see how well they meet the system’s performance and cost goals. This paper proves that the System Design Problem is NP-complete by red...