# Questions tagged [ds.algorithms]

Questions regarding well-defined instructions for completing a task, and relevant analysis in terms of time/memory/etc.

1,577 questions
117 views

### Is there any time efficient way of achieving the result of FKS hashing lemma?

FKS hashing lemma states. Given a set of $n-$bit numbers $\{x_1,x_2,\dots,x_k\}$ there exist a prime $p$ of $O(\log n + \log k)$-bit such that $x_i$ mod $p \neq$ $x_j$ mod $p$ if $x_i \neq x_j$...
90 views

### Minimizing SubModular Function: Cardinality

Given a submodular function f: 2^V to reals (not necessarily monotone), and an integer k, find a set S such that |S| <= k and such that f(S) is minimized. When the size constraint is |S| >=k, the ...
58 views

### What is the fastest gradient based algorithm to get to criticality of a “nice” non-convex function?

I am allowing for the following properties for a once differentiable non-convex $f : \mathbb{R}^d \rightarrow \mathbb{R}$, (a) Let there be a $\sigma >0$ s.t the norm of the gradient of the ...
488 views

### Minimum cost topological ordering

We are given a $n$ vertex directed graph $G=(V,E)$ and also given a cost function $c:V\times [n]\to \mathbb{R}$. Consider a topological ordering of the vertices, $v_1,\ldots,v_n$, the cost of the ...
150 views

### What is the fastest known algorithm for finding conjugacy classes?

Given a finite group $G$ of size $n$ by the table representation. I want to compute the conjugacy classes of group $G$. A trivial algorithm seems to take $O(n^2)$ operation ( $b = g^{-1}a g$ type ...
165 views

### Find a pair of nodes with maximum sum of distances in k given trees

For k edge-weighted trees $T_1,T_2...T_k$ which contain the same set of nodes $\{1,2,... n \}$, I want to find a pair of nodes $(x,y)$ which maxifies $$\sum_{i=1}^k d_i(x,y)$$ where $d_i(x,y)$ ...
98 views

### Graph-related applications of the fast Fourier transform (and other algebraic algorithms)

The fast matrix multiplication algorithm is useful for numerous graph problems (e.g. matchings and shortest paths). However, while the fast Fourier transform algorithm implies several other near-...
135 views

### Efficient algorithm for generating data dependency DAG from lists of memory ranges and access modes

Assume you are given: A list of N (not necessarily distinct) memory ranges of the form [x,y], where x and y are non-negative integers representing the lower and upper bounds of the range, and A list ...
53 views

### Has Khachiyan/Porkolob's convex integer optimization been implemented?

Khachiyan and Porkolab in 'Integer optimization on convex semialgebraic sets' gave an $O(ld^{ O(k^4)})$ algorithm to minimize a degree $d$ form with integer coefficients of binary length at most $l$ ...
354 views

### Is abelian group isomorphism in $\mathsf{AC^0}$?

An $O(n^2)$ running time algorithm for abelian group isomorphism is easy to see. Later working on this problem in 2003 Vikas improve the result from $O(n^2)$ running time to $O(n \log n)$. In 2007, ...
202 views

634 views

### Can neural networks be used to devise algorithms?

After the newer and newer successes of neural networks in playing board games, one feels that the next goal we set could be something more useful than beating humans in Starcraft. More precisely, I ...
114 views

### Continous work distribution algorithm with failover

Imagine there's a system where there's N workers and M units of work, for example, N ≤ 64, M = 256. Is there an algorithm that ...
122 views

### Convention for RAM machine models

When algorithm asymptotic runtimes are given without explicitly noting the computational model, what is the convention for the exact model used? My understanding is that most problems use unit-cost ...
70 views

### Number of maximally different DAG's in a digraph?

Given a digraph $\overrightarrow{G}$, I'm interested in extracting all DAGs from $\overrightarrow{G}$ such that: Each DAG's vertices are differently sorted, Each DAG is maximal (adding any extra ...
443 views

### Does there exist an ontology for algorithms?

It appears that algorithmic complexity theory has already figured out Kolmogorov complexity, when applied to representations of programs themselves, can already serve as a solid theoretical metric of ...
132 views

### Computing size of permutation group from generators

You're given $k$ permutations $a_1,\dots,a_k$. Consider closure of this set under the composition operation. What are most efficient and simple algorithms to calculate the size of this closure?
74 views

### Data structures for subset and superset queries over a set of multisets

I am interested in papers discussing efficient data structures for storing and querying a set of multisets. I am particularly interested in the following two operations: Subset query: retrieve all ...
308 views

### Algorithm to compute distance between powers

Given coprime $a, b$, can you quickly compute $$\min_{x, y > 0} |a^x - b^y|$$ Here $x, y$ are integers. Obviously taking $x = y = 0$ gives an uninteresting answer; in general how close can these ...
90 views

### What are some techniques for “balancing” a tree beside heavy-light and centroid decomposition?

The only techniques i know are those in the title.
174 views

### Complexity of the mandelbrot set on rationals

(Also posted on mathoverflow) Given two rationals $a,b \in \mathbb{Q}$, call $c = a + ib$, i.e., the complex number represented by these two rationals. A point $c$ is contained within the Mandelbrot ...
341 views

### Amortized analysis of red-black trees

Is there an analysis of red-black trees using amortized analysis? I saw it mentioned somewhere as an example of amortized analysis but all the proofs that I know use a global approach ("black height") ...
56 views

### \alpha-path on Euclidean graphs

Consider the following problem: Suppose we are given a G=(V, E) Euclidean Graph in the plane and a real $\alpha > 0$. For simplicity assume, there exists only one path whose summation of weights ...
59 views

201 views

### Understanding performance of QFBV SMT solvers

SMT solvers such as Z3 or Boolector use a complex set of heuristics to solve problems. However, this also makes predicting the performance of such a solver for a given problem very hard. My question ...
112 views

113 views

### Different algorithms for longest increasing subsequence

The longest increasing subsequence problem has a simple and elegant $O(n \log n)$ time solution via patience sorting. Such a basic and well-studied problem, however, should have a number of different ...
162 views

### What exactly did Lenstra prove on mixed integer linear program?

I studied Lenstra's paper https://www.jstor.org/stable/3689168. I have no clue what complexity he provides on Mixed Integer Programming (it is too terse and it is not a stand alone paper as he assumes ...
179 views

### Cases of Linear programming known to be in $NC$?

Linear programming is $P$-complete. However are there special situations where we know an $NC$ algorithm?
59 views

### Complexity of Finding Optimal Synergistic Set Packings

Motivation: While developing tools for fast execution of machine learning workflows, we realized that many workflows require intermediate results -- sometimes we should cache these results, and ...
760 views

### Minimal Cost of Eulerian Path

Problem: Given a planar (undirected and mostly sparse) graph with an Eulerian Path, we introduce a cost function f: (v, e1, e2) for all two edges e1 and e2 that share a vertex v. The function also ...
### On permanent mod $3^t$ computation
By $'$ I mean transpose. I gather the info here from rjlipton.wordpress.com/2014/12/21/modulating-the-permanent. We know that if $U\in\Bbb F_{3^t}^{n\times n}$ satisfies $UU'=I_n$ in $\Bbb F_{3^t}$ ...