All Questions
Tagged with combinatorial-optimization computational-complexity
42 questions
3
votes
2
answers
336
views
Algorithm to evaluate "connectedness" of a binary matrix
I have the following problem: given an $m \times n$ binary matrix $A$ like e.g. the following $9 \times 39$ matrix:
...
- 5,429
0
votes
0
answers
92
views
Algorithm that can solve or approximate the solution to a combination problem
I have a computational problem on my hands and I would like your help.
Here is my problem (simplified)
Let $X = \{x_1, x_2, \ldots, x_n\}$ represent a set of $n$ values.
Each value $x_i$ has a ...
- 869
0
votes
0
answers
16
views
Complexity of finding single source paths with capacity constraints and length constraints
Let $G=(V,A)$ be a directed graph with distinguished vertex $s\in V$ and let $c:A\rightarrow{\mathbb N}$ denote arc capacities. For any $t\in V,t\not=s$ we are given two numbers: $C_{t},L_{t}$. Let $...
- 21
1
vote
0
answers
51
views
Hardness of an optimization problem when some variables are fixed
Given a general optimization problem, I would like to know what we can say about the hardness of the problem when a subset of its variables are fixed.
With the two (related) examples, it is clear that ...
- 6,367
3
votes
1
answer
214
views
NP-hardness of finding maximum of minimum element in diagonal of a matrix
For $A = \{a_{ij}\} \in R^{n\times n}$, is finding
$$
\max_{\sigma \in S_n}\min_{1 \le i \le n} a_{i,\ \sigma_i}
$$
NP-hard?
- 32.1k
2
votes
1
answer
175
views
Optimization over permutation
The Problem
This is the problem I am working on: Given a set $X = \{x_1, x_2, \cdots , x_n\}$ in a metric space, find an optimal ordering $\pi : X \rightarrow X$ that maximizes the following objective ...
- 5,429
5
votes
1
answer
291
views
Minimum number of edges to remove to have low degree
I have the following problem, where $k$ is a fixed integer.
Input: Graph $G$.
Output: Minimum number of edges to remove from $G$ to obtain a graph such that every node has degree at most $k$.
Do ...
- 32.1k
1
vote
0
answers
101
views
On determinant and permanent of certain homotopy defined simple matrices
Let $A_1,A_2,B_1,B_2$ be four $n\times n$ $0/1$ square matrices where $$\det(A_1)=\det(A_2)=per(A_1)=per(A_2)=1$$
$$\det(B_1)=\det(B_2)=per(B_1)=per(B_2)=0$$
hold ($per$ refers to permanent).
I. What ...
- 13.9k
3
votes
1
answer
344
views
How to find the maximum of a sum of squares of sums?
Is there any better than a brute force method for finding the maximum
$$\max\limits_{ (d_{1},\dots,d_{n}) \in \mathbb Z_{m}^{n}} \sum_{j=0}^{m-1} \left(\sum_{i=1}^{n}v_{i,(j+d_{i})\bmod m}\right)^{2}$$...
- 5,429
7
votes
1
answer
171
views
Metric TSP with integer edge cost
Given a metric TSP with integer edge cost upper-bounded by a constant $C_{\max}$, can we find an poly-time algorithm solving this TSP instance?
- 32.1k
5
votes
0
answers
240
views
Existence of $\{0,1\}$-solution to a system of linear equations with coefficients in $\{0,1\}$
Crossposted at Theoretical Computer Science SE
A problem I study reduces to a system of linear equations $A\mathbf{x}=\mathbf{1}$ where $A$ is an $m\times n$ matrix with each entry $a_{ij}\in\{0,1\}$....
0
votes
1
answer
128
views
What is the computational complexity of the calculation of $ \Psi(x) $?
What is the computational complexity of the calculation of $ \Psi(x) $ described below:
Let $\left\{ f_i : \{0,1,\dots,m\} \to \mathbb{R} \right\}_{i=1}^n$. For each $x \in \{0,1,\dots,m\}$ we ...
- 5,429
0
votes
0
answers
26
views
Complexity of heaviest 2-optimal vertex-disjoint cycle covers
Calculating lightest vertex-disjoint cycle covers of finite complete symmetric graphs with weighted edges can be done efficiently and also renders the edge set of the calculated cycles free of pairs ...
- 13.2k
0
votes
1
answer
354
views
Maximize sum of edge weights on spanning tree
Problem: Given a complete graph with n vertices, the edge weight between vertex $i$ and vertex $j$ is $b[i]\times b[j]$.
Under the condition that the degree of point $i$ on spanning tree is DEG $[i]$, ...
- 5,429
2
votes
0
answers
33
views
Algorithm for lightest unnested planar vertex-disjoint cycle-cover
Question:
given a finite set $\mathcal{P}$ of disjoint points in the Euclidean plane and the set $\mathcal{C}$ of all simple polygons whose corners are subsets of $\mathcal{P}$,
what is the ...
- 13.2k
2
votes
0
answers
62
views
A combinatorial question about encoding the subsets of logarithmic-bounded cardinality
Let $k \in \mathbb N - \{0\}$ and $f(n) = \binom n 0 + \binom n 1 + \dotsc + \binom n {\log^k n}$.
Our question is:
$f(n) = o(2^{\log^{k+1} \ (n)})$ or $f(n) = \Theta(2^{\log^{k+1} \ (n)})$, which ...
- 193
2
votes
0
answers
27
views
Complexity of weighted fractional edge coloring
Given an edge-weighted multigraph $G=(V,E)$ with a positive, rational weight function $(w(e): e \in E)$, the weighted fractional edge coloring problem (WFECP) is to compute ($\min 1^T x$ subject to $...
- 3,486
3
votes
1
answer
262
views
What is known about this TSP variant?
Euclidian (planar) TSP asks for a tour with the minimum total length. The problem is known to be NP-hard. I am interested in the variant of finding a closed tour with the minimum enclosed area (...
1
vote
0
answers
57
views
On divisibility conditions implying local coprimality conditions
This question is inspired by Bernardo Recaman's question Strings of consecutive integers divisible by 1, 2, 3, ..., N on intervals of $n$ integers being divisible by the integers $1$ through $n$. The ...
- 13k
1
vote
1
answer
82
views
The complexity on calculation of the Graev metric on the free Boolean group of a metric space
For a set $X$ by $B(X)$ we denote the family of all finite subsets of $X$ endowed with the operation $\oplus$ of symmetric difference. This operation turns $B(X)$ into a Boolean group, which can be ...
- 1,528
1
vote
0
answers
37
views
Fast certficate of negativity for objective value of mixed-integer linear program
Let $c \in \mathbb R^n$, $A \in \mathbb R^{m \times n}$, $b \in \mathbb R^m$, and $I \subseteq \{1,2,\ldots,n\}$. Consider the Mixed integer linear program (MILP)
$$
\begin{split}
f^* = &\max \; ...
- 6,853
1
vote
0
answers
70
views
Shortest Lattice Vector with restricted $x$
Let $\Lambda$ be a lattice with basis, $B$ consisting of vectors $b_i$, so that the elements of $\Lambda$ are of form, $y\in \Lambda \iff y=Bx=\sum_i b_ix_i$ for some $x_i\in\mathbb{Z}$.
My questions ...
- 1,096
0
votes
1
answer
140
views
Maximum partition of bipartite graph
Let $G = (U, V, E)$ be a bipartite graph. Let $w: E \to \mathbb{R}$ be a weight function on the edge set $E$. Given subsets $U_1,\ldots, U_k \subset U, U_i\cap U_j = \emptyset$ and a partition $V_1,\...
- 34.3k
1
vote
0
answers
140
views
Is the partition of bipartite graphs NP-hard?
I wonder if the following problem is NP-hard. Is it?
Given a bipartite graph $G = (U, V, E)$ with weights $w : E \to \mathbb{R}_+$, find a partition of $U$ into $U_1, U_2$ and nonempty disjoint ...
3
votes
1
answer
186
views
Algorithms for Fixing Sudokus
Suppose someone got stuck solving a Sudoku and asks you to figure out, what went wrong. Unfortunately that person only sends you a copy of the instance, where you neither see which of the numbers ...
- 361
16
votes
2
answers
603
views
NP-hardness of finding 0-1 vector to maximize rows of {-1, +1} matrix
Consider the following discrete optimization problem: given a collection of $m$-dimensional vectors $\{ v_1, \dots, v_n \}$ with entries in $\{-1, +1\}$, find an $m$-dimensional vector $x$ with ...
- 61.9k
1
vote
0
answers
49
views
Cost associated set problem NP-hard
I have the following problem. I wonder whether or not it appears in the literature. Is it NP-hard?
Given a set $S = \{1,2,\ldots,m\}$, and $A_1,\ldots, A_n$ are subsets of $S$. Each set $A_i$ has ...
CommunityBot
- 1
6
votes
1
answer
336
views
Is this problem of selecting points NP-hard?
I have an optimization problem related, in a certain way, to the expression of a set of points with the least number of points and I don't know if it is NP-hard (or not).
More formally, I have a ...
- 5,590
2
votes
1
answer
188
views
$0/1$ programming multiple quadratic constraints
If we have an $n$-variable rank $n$-linear system it is clear we can find whether there exists a $0/1$ solution in polynomial time.
If we have an $n$-variable degree $2$ system how many constraints ...
CommunityBot
- 1
2
votes
1
answer
111
views
NP-Hardness of finding minimal-support solutions of underdetermined systems over any field
Given a field $\mathbb{F}$ and a consistent underdetermined system $Ax=b$ over $\mathbb{F},$ $A\in \mathbb{F}^{m \times N}$ and $b \in \mathbb{F}^m,$ finding a vector $z \in \mathbb{F}^N$ such that $...
CommunityBot
- 1
1
vote
1
answer
206
views
Show $0-1$ Knapsack is polynomially reducible to this problem
I have already posted this question here but have not received an answer so I am cross-posting with hope to reach a larger amount of mathematicians:
Let $T=\{1,\cdots,n\}$ and consider the ...
CommunityBot
- 1
1
vote
0
answers
153
views
NP-Hardness of Underdetermined Systems over $F_2$ implies the same for $F_{p^q}$
Assume that the yes-no problem of whether $x' \in F_{p^q}^{n}$ is a minimal support solution for a consistent underdetermined system $Ax=b,$ $A \in F_{p^q}^{m \times n}, b \in F_{p^q}^n$ is an NP-hard ...
- 259
1
vote
0
answers
1k
views
Number of different combinations in a 0-1 knapsack problem with integer weights [closed]
My question is actually very similar to this other one: Given a vector of positive integers, count the number of combinations which have a sum that produces a different value. But, since this previous ...
CommunityBot
- 1
1
vote
1
answer
332
views
Graph colouring for bounded degree graphs
I'm fairly new to colourings on bounded degree graphs i'm interested in the following questions,
For planar graphs with bounded degree $4$ is finding the colouring number $NP$-hard? So is ...
- 25.4k
1
vote
2
answers
256
views
Maximum subgraph edge distance greater than given number
I have a weighted graph G with approximately 75000 nodes. I would like to find subgraph G' induced on a subset of nodes, such that all edge weights in G' are greater than a given constant C and the ...
- 32.1k
4
votes
0
answers
175
views
What is known about the complexity of this covering problem?
Let $G=(V,E)$ be a graph. A vertex set $X\subseteq V$ is called critical if $X\neq\emptyset$ and no vertex in $V\setminus X$ is adjacent to exactly one vertex in $X$. The problem is to find a vertex ...
CommunityBot
- 1
4
votes
2
answers
242
views
Complexity of finding the maximum sum divided by product
What is the complexity of the following optimization problem?
Problem.
Given $n$ pairs of positive reals $(a_i,b_i)_{i=1}^n$, choose a subset $S \subseteq [n]$ to maximize
$$
\frac{\sum_{i\in S} a_i}{...
- 2,286
2
votes
2
answers
202
views
Combinatorial optimization problem involving infinite spin system
In material science research, I am developing an algorithm to solve an infinite combinatorial optimization problem which I believe is the most natural problem when the system size goes to infinity.
...
1
vote
1
answer
131
views
A certain instance of the Set Covering problem
Is there any useful structure associated with the following instance of the Set Covering problem?
Let $G$ be a weighted graph and let $\mathcal{P}$ denote the set of all shortest paths between all ...
3
votes
1
answer
509
views
Application of Combinatorics, Logic and computability theory in physical science: Tiling of Wang Tile with proportionality
The original problem of Domino Tiling and Wang Tile has great theoretical interest on computability theory... However, the great emerging problem on application of Wang Tile in material science and ...
CommunityBot
- 1
6
votes
1
answer
1k
views
Best ranking in tournament: polynomial time algorithm?
This question was posed by my colleague Torbjörn Lundh in his paper Which Ball is the Roundest? A Suggested Tournament Stability Index, Journal of Quantitative Analysis in Sports 2(3), 2006. We have ...
- 940
0
votes
0
answers
79
views
Approximation for accumulative set cover
Let $S_1,\ldots,S_m\subseteq U$ be subsets of a set $U$ of size $\lvert U\rvert=n$. Over all permutations $\pi$ of the set $\{1,\ldots,m\}$, I want to maximize the quantity
\begin{equation}
\sum_{k=1}...
- 2,966