Walsh [Wal10, Wal09], Davies et al. [DKNW10, DKNW11], and Narodytska et al. [NWX11] studied various voting systems empirically and showed that they can often be manipulated effectively, despite their manipulation problems being NP-hard. Such an experimental approach is sorely missing for NP-hard control problems, where control refers to attempts to tamper with the outcome of elections by adding...

After Cook’s paper [Coo71] published, Dick Karp immediately realized that the notion of NP-hardness captures a large amount of intractable combinatorial optimization problems. In [Kar72], he showed 21 problems to be NP-complete. This list quickly increased and by the time of 1979, Garey and Johnson [GJ79] wrote a whole book on NP-complete problems. This book has became a classic nowadays, and t...

multi-criteria shortest path problems (mspp) are called as np-hard. for mspps, a unique solution for optimizing all the criteria simultaneously will rarely exist in reality. algorithmic and approximation schemes are available to solve these problems; however, the complexity of these approaches often prohibits their implementation on real-world applications. this paper describes the development ...

flow shop sequencing problem is included in np-hard problems and a number of heuristic methods have been developed to solve it. most of these methods are offered for the crisp processing time. however fuzzy algorithm is appropriate for the problems with fuzzy processing time. this paper presents a method in which an algorithm is used to minimize make span of flow shop with fuzzy processing time...

This paper investigates the complexity of the min-max and min-max regret assignment problems both in the discrete scenario and interval data cases. We show that these problems are strongly NP -hard for an unbounded number of scenarios. We also show that the interval data min-max regret assignment problem is strongly NP -hard.

We show it is NP-hard to pack the maximum number of segments in a convex 3-dimensional polytope. We show this packing problem is also NP-hard for general polygonal regions in the plane. This problem relates two streams of research, Kakeya set problems and packing problems.

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...

All of CS161 and the first half of CS261 focus on problems that can be solved in polynomial time. A sad fact is that many practically important and frequently occurring problems do not seem to be polynomial-time solvable, that is, are NP -hard. As an algorithm designer, what does it mean if a problem is NP -hard? After all, a real-world problem doesn’t just go away after you realize that it’s N...

Computing the clique number and chromatic number of a general graph are well-known to be NP-Hard problems. Codenotti et al. (Bruno Codenotti, Ivan Gerace, and Sebastiano Vigna. Hardness results and spectral techniques for combinatorial problems on circulant graphs. Linear Algebra Appl., 285(1-3): 123–142, 1998) showed that computing the clique number and chromatic number are still NP-Hard probl...

In this paper, we first introduce a generalized version of open shop scheduling (OSS), called generalized cyclic open shop scheduling (GCOSS) and then develop a hybrid method of metaheuristic to solve this problem. Open shop scheduling is concerned with processing n jobs on m machines, where each job has exactly m operations and operation i of each job has to be processed on machine i . However...