Questions related to NP-hardness and NP-completeness.

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Proving NP-hardness of scheduling problem (total weighted completion time)

Consider the problem $P \mid \mid \sum w_j C_j$. I want to prove that this problem is (strongly) NP-hard by reducing from $3$-Partition, but I am not really sure how to do this. Just to be precise, ...
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35 views

Problems needs solutions in Distributed computing?

This is same as question. The answer for the question is 3 years old. Since the old topics will be quickly outdated or solved and new research problems arises, it would be great to know the latest ...
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0answers
69 views

Can a search problem be NP-hard? [migrated]

The common examples of NP-hard problems (clique, 3-SAT, vertex cover, etc.) are of the type where we don't know whether the answer is "yes" or "no" beforehand. If we have an NP problem where know that ...
11
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2answers
1k views

To which complexity class does this language belong?

I was thinking about which class this language belongs: $L =\{ \langle G,k \rangle \mid G $ is a graph, $k$ is a natural number and $k$ is the chromatic number of $G\}$ I thought of $L$ as (1) " ...
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0answers
28 views

Hardness of Minimizing Submodular Functions with Cardinality Constraints

I am new to submodular functions and I am reading the introductions to submodular functions and applications ( https://www.ima.umn.edu/optimization/seminar/queyranne.pdf ). In this introduction, it ...
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1answer
172 views

$k$-clique in $k$-partite graph

Is the decision whether a $k$-clique exists in a $k$-partite graph NP-hard? I have found only a very limited number of references on this problem, and they seem to be concerned with heuristics to ...
4
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1answer
76 views

Generalized geography on solid grid graphs

A post here For which families of graphs is Generalized Geography in $P$? mentioned that generalized geography on solid grid graphs is open. Is the question still open? A quick search on Google shows ...
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1answer
223 views

NP-complete problems with optimal approximation in poly-time

I'm looking for examples of hard optimization problems, for which we have an optimal approximation (not that this is not the same as $PTAS$, as we require a completely tight approximation, and not ...
4
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1answer
335 views

The complexity of a multi-objective shortest path problem

I have the following shortest path problem. Consider a directed graph with $n$ levels. Each level has $m$ nodes. Each node at level $i$ is connected to all nodes at level $i+1$. Let us also make a ...
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0answers
63 views

Finding exact value with a quotients of products of random values

Sorry for the haphazard title: really not sure what this should be called Suppose we have a set of $z$ random values $S = r_1, \dots, r_z$ drawn from $\mathbb{Z}_N$ (where $N$ is some large prime). ...
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3answers
247 views

Minimum vertex cover on k-regular graphs, for fixed k>2 NP-hard proof?

Good Evening! I am aware that the minimum (cardinality) vertex cover problem on cubic graphs ($3$-regular) graphs is $NP$-hard. Say positive integer $k>2$ is fixed. Has there been any ...
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3answers
158 views

How hard is it to find a “well-distributed” subset of models of a propositional formula?

We consider the propositional language $\mathcal{L}_{\mathit{PS}}$ defined over a finite alphabet $\mathit{PS}$ and the usual logical connectives. An interpretation is an assignment $\mathit{PS} ...
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1answer
312 views

“Snake” reconfiguration problem

While writing a small post on the complexity of the videogames Nibbler and Snake; I found that they both can be modeled as reconfiguration problems on planar graphs; and it seems unlikely that such ...
7
votes
1answer
346 views

Does $NP$-hardness of $c$-approximation (for some $c>1$) imply $APX$-hardness?

Assume that for a given minimization problem with only integer solutions, it is $NP$-hard to decide if the optimal solution is 5 or 6. I.e., a polynomial-time algorithm with an approximation ratio ...
6
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0answers
106 views

Maximum weight “fair” matching

I'm interested in a variant of the maximum weight matching in a graph, which I call "Maximum Fair Matching". Assume that the graph is full (i.e. $E=V\times V$), has even number of vertices, and that ...
2
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2answers
172 views

Balls & Bins: A punishment and reward game

Consider a game where one has a set of bins $(b_1, b_2, ...)$, and each bin has an associated initial count of balls $(c_1, c_2, ...)$. The rules of the game are as follows: (1) Once a bin has a ...
2
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0answers
72 views

Calculating the ground state of an Ising model with $\sigma_i = (0,1)$ spin state assignments (do Barahona & Istrail's NP-hardness results hold?)

In a typical Ising model, one has possible spin assignments of $\sigma_i = \pm 1$. However, one can also imagine a $q = 2$ Potts model generalization with spin assignments $\sigma_i = (0,1)$. Is ...
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56 views

Reconstructing labeled poset from linear extensions

Let $(P, <, \mu)$ be a labeled poset, that is, a partial order $(P, <)$ with a labeling function $\mu$ that maps the elements of $P$ to labels in an alphabet $\Sigma$. A label list (or word) is ...
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0answers
108 views

Advances towards proving the Held-Karp conjecture for TSP

I've only began my research into the Held-Karp conjecture and I was wondering about recent progress in proving the conjecture. The Held-Karp relaxation is conjectured to have an integrality gap of ...
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0answers
59 views

Trying to find polynomial-time algorithms for knapsack-like problems

Consider two related problems: You have n cannisters that must go into m trucks that can each carry k cannisters. You require that no truck becomes overloaded, and for each cannister, there is a ...
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0answers
65 views

Which complexity information of Ising model is more important?

In 1982, Barahona proved that finding the ground state of an Ising model is NP-hard. Later, in 2000, Istrail proved that it is NP-complete. When I look up the citations of these two papers using ...
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0answers
45 views

Bounding the cost of an approximation algorithm when subtraction involve [closed]

Given an algorithm with approximation ratio $\alpha$, and another algorithm with approximation ratio $\beta=n^\epsilon$, and a solution to a problem with cost $c$. What is the standard way to bound ...
4
votes
2answers
128 views

Variation on partial Set Cover with penalties

I'm looking at the following problem, which I'm hoping is perhaps a known variant of the Set Cover problem: Input: We're given a universe $U$ and two disjoint subsets $A$ and $B$ such that $A \cup ...
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0answers
67 views

Minimum Weight Ordering of nodes on a directed graph

I'm bumping my head against the wall trying to prove this problem is NP-complete (it might not be) Let $G = (V,E)$ be a directed graph with weights $w:E \to \mathbb{R_{\geq 0}}$ on the edges. The ...
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0answers
52 views

Minimum vector sets span spaces cover problem

Instance: a set of vectors $V=\{\mathbf{v}_1,\mathbf{v}_2,...,\mathbf{v}_n\}$ and $m$ vector sets $V_1,V_2,...,V_m$, each of which contains multiple vectors ($V_i$ may not be a subset of $V$). In our ...
4
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1answer
118 views

Inapproximability of $(\alpha, \beta)$ bi-criteria approximation

An $(\alpha, \beta)$ bi-criteria approximation algorithm for $k$-center is defined as an algorithm that returns a solution whose value is $\beta \cdot OPT$ ($OPT$ being the optimal solution for the ...
10
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1answer
333 views

Probability of generating a desired permutation by random swaps

I'm interested in the following problem. We're given as input a "target permutation" $\sigma\in S_n$, as well as an ordered list of indices $i_1,\ldots,i_m\in [n-1]$. Then, starting with the list ...
6
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0answers
209 views

NP-hardness of tasks graph assignment to two heterogenous servers

I have a problem with determinig if the following assignment problem is NP-hard. Any comments and suggestions would be appreciated. Problem definition Given is a directed acyclic graph $G=(V,E)$ ...
1
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1answer
90 views

Node-weighted steiner problem with few terminals

Consider the node-weighted steiner problem: Input: a graph $G=(V,E)$, a set $T\subseteq V$ of terminals, a weight function $w: V\setminus T \to \mathbb{R}_+$. Output: a minimum weight ...
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0answers
145 views

Definition of Planar 3-SAT

What is the standard definition of Planar 3-SAT? I have seen a number of different definitions. What was the original paper that defined it and proved it to be NP-complete?
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1answer
134 views

Hardness of an extended maximum set packing problem

(Edited) The maximum set packing problem when the sets are all of equal size, say $k$, is known to be NP-hard for $k \ge 3$. The requirement in this problem is that the sets in the solution will be ...
2
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1answer
140 views

Complexity class of a subset problem similar to subset sum

What could be the complexity class of the following problem: Given a positive integer $K$, a positive integer $d$ (say $2$) and a set $S$ of all non-negative integers less than $K$ find a $S' ...
12
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2answers
1k views

Hamiltonian cycle on graphs without small cycles

While answering this question on cstheory, I (informally) proved on the fly the following theorem: Theorem: For any fixed $l \geq 3$ the Hamiltonian cycle probem remains NP-complete even if ...
6
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0answers
87 views

Hard extendability problems

In extendability problem, we are given part of the solution and we want to decide whether we can extend it to a complete solution. Some extendability problems are efficiently solvable while other ...
5
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0answers
179 views

NP-completeness of the Dominating set problem for planar graphs of maximum degree 3?

I am trying to learn about some techniques that are used for proving the NP-completeness of domination related problems. One of the problems that is known to be NP-complete is the domination number of ...
3
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1answer
296 views

Hardness of 3-dimensional matching variant

I am thinking about a variant of 3-dimensional matching. In normal 3d matching, we have three sets of vertices $X$, $Y$ and $Z$, and a set of edges $E \subseteq X \times Y \times Z$. We want to choose ...
2
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1answer
120 views

NP-hardness of a bilinear program?

Given $a_i, b_i, c_i, d_{ij}\in [0,1]$ for $i,j\in [n]$ and $i\neq j$ such that $\sum_{i\in [n]} a_i=1$ and $d_{ij}=d_{ji}$. I have the following bilinear program: max $\sum_{i=1}^n (x_i-a_i)y_i$ ...
2
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0answers
122 views

Graph partition with objective over intra-partition weights

I have a problem in which I need to find an optimal graph cut that maximizes an objective over weights not on the cut. I have looked at the literature but have not been able to find any similar ...
1
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0answers
52 views

Help in NP-Hardness proof of a certain type of Class Cover problem

Class Cover Problem is nothing but finding an optimal cover of certain class (Point Set) with a particular shape only i.e. finding minimum number of a certain shaped polygon (for example, rectangle) ...
2
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1answer
121 views

Set cover with budget on sets

I am wondering if this is a studied variant of the Set Cover problem. We are given a universe $X$, a collection of sets $S = \{S_1, ..., S_m\}$ and integers $c_i$. We want to cover all elements in ...
7
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1answer
270 views

NP-hardness proof: looking for some good restricted np-hard problems

To show the NP-hardness of a problem, one need to choose a known NP-hard problem and find a polynomial reduction from the known problem to his problem in hand. Theoretically, any NP-hard problem can ...
2
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2answers
236 views

For which values of $k$ is the $k$-disjoint paths problem in $\mathcal{P}$?

The $k$-Vertex-Disjoint Paths Problem ($k$-$\text{DPP}$) is defined as follows: Input: A graph $G=(V,E)$ and $k$ pairs of vertices $(s_1,t_1),\ldots,(s_k,t_k)$. Question: Does there exist ...
6
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3answers
450 views

Multidimensional knapsack STRONGLY NP-complete

Who can point me to a reference where it is actually shown that multidimensional knapsack is strongly NP-complete? I have found loads of papers where they claim it is, without citation; I have found ...
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0answers
59 views

Different hardness proofs w.r.t different classes

Consider a language $L$ which is hard for some class $C$ (e.g. PSPACE-hard). Trivially, $L$ is also $D$-hard for every class $D\subseteq C$ under the same type of reduction (e.g. NP-hard). Is there a ...
6
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1answer
278 views

Max-weight connected subgraph problem in planar graphs

The maximum-weight connected subgraph problem is as follows: Input: a graph $G=(V,E)$ and a weight $w_i$ (possibly negative) for each vertex $i \in V$. Output: a maximum-weight subset $S$ of ...
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1answer
91 views

NP Hardness of Metric Steiner Tree

It is known that the metric steiner tree problem is NP hard (Garry and Johnson [1977]). I wanted to know if there is a simpler way of proving the same. Specifically, I am trying to find a polynomial ...
7
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0answers
137 views

What relations are there between a problem hardness and the hardness of verifying a witness?

I had some hard times trying to formulate the question, so I'll start with some examples: Suppose you are given a Dominating Set instance, $<G,k>$. Now suppose I give you a set of vertices $D$ ...
4
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0answers
181 views

How does part 5 of the paper “computational complexity of Minesweeper” work?

Marzio De Biasi mentioned this paper in this answer, and that paper's claim in part 5 would appear to resolve my question. However, there seems to be a significant gap in the proof. Even though one ...
6
votes
1answer
347 views

Is it NP-hard to _play_ minesweeper perfectly?

This paper shows that it is NP-hard "to determine if there is some pattern of mines in the blank squares that give rise to the numbers seen." If there is a way to "lead a perfect player into" such ...
4
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0answers
126 views

another solution problem (ASP) of integer multicommodity flow: is it NP-complete?

I know that integer multicommodity flow is NP-complete. It was proven in "On the complexity of time table and multi-commodity flow problems" (http://dl.acm.org/citation.cfm?id=1382492) that any SAT ...