# Questions tagged [algorithms]

An algorithm is a sequence of well-defined steps that defines an abstract solution to a problem. Use this tag when your issue is related to design and analysis of algorithms.

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### Improve algorithmic complexity

We have an array of N size. We have to perform Q queries on it, in which each Query contains and Index I for which we do: ...
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### Need help analyzing the runtime analysis of this algorithm/algorithms in general

This is the algorithm I was trying to find the runtime of (doSomething) - ...
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### Time interval correction for step detection algorithm

I am currently going over this paper, and in fact have already tried to implement it: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4634483/ [1] Paper looks at the amplitude of the step and the time ...
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### Multiplication mod 2 without extra registers

For an arbitrary bitstring $(x_1, x_2,\ldots, x_n)$ and an $n\times n$ invertible binary matrix $M$ (fixed ahead of time), I would like to construct a circuit $C$ acting on these $n$ bits whose output ...
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### Equation for optimization problem in linear programming

Suppose that you are trying to solve the optimization problem: Maximize v⋅x subject to Ax ≥ b for some A∈R^(m×n) (i.e. trying to solve an optimization problem in n variables with m linear inequality ...
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### Reducing Kleene's predecessor for Church numerals

I am trying to "reinvent" Kleene's predecessor myself. The following code snippet should be self-explanatory. The idea is to make a 2-tuple and count up from zero, i.e. ...
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### How to get synonyms from definitions using Bayes algorithm

I work on a project: an online dictionary where the user can find definitions of a word he's looking for. My supervisor asked us to add synonyms using machine learning. He recommend us to use Bayes ...
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### $\Omega(m)$ and $O(m)$ meaning in theorem proof about dynamic array complexity

My algorithms and data structures' book states that to create a dynamic array the following procedure is followed: Let $d$ be the length of an array $a$ and $n$ the number of elements stored in ...
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### Options for approaching stable marriage problem with unequally sized sets of elements/preferences

I am looking for an algorithm/code that will provide stable matching for two unequally sized sets of elements (clubs and students) with an unequal set of preferences. There is a large pool of students ...
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### Floyd's cycle detection algorithm, why is it linear time, and how do you prove that tortoise and hare will meet?

I haven't been able to find a full proof of Floyd's cycle detection algorithm. All proofs that I have been able to find just explain why the distance from the start of the graph to the start of the ...
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### Fault localisation using model checking

In many papers like Empirical Evaluation of the Tarantula Automatic Fault-Localization Technique there is a good explanation about how tarantula algorithm can be used with test suits. Is there any ...
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### Exit Condition for Knight's Tour Using Depth-First Search

Suppose I'm using the algorithm below to perform Depth-First Search in a 2d Grid. It seems like it should be possible to adjust it to perform a Knight's Tour with little change. For example I would ...
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### Algorithms that run in polynomial time if P=NP

On Wikipedia, it says that that there are some algorithms that would run in polynomial time if and only if P=NP. They gave one example (without citation), but are there any others? I tried looking ...
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### Efficient algorithm for retrieving the transitive closure of a directed acyclic graph

I'm trying to solve a graph problem (it's not for homework, just to practice my skills). A DAG $G(V,E)$ is given, where $V$ is the set of vertices and $E$ the edges. The graph is represented as an ...
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### What is an algorithm to find the largest rectangle of white space in an image?

Take an image, (the Google home page) is a good example. I want an algorithm to find the largest white rectangle in this image. That is to say, the largest rectangle that would fit in an area of ...
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### Algorithm For Random Distribution of Prizes Over A Given Time Period

I have been assigned a task to come up with an algorithm for evenly distributing prizes over a given time frame, I am looking for advice as I am a bit stumped on where to start. Here are my ...
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### Can I find all the common subsequences between 2 sequences by using dynamic programming?

I need to know if there's a dynamic programming algorithm that returns all common subsequences between 2 sequences not just the longest one. Thank you.
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### What's an efficient algorithm to calculate line breaks (word wrap) for balanced widths (minimum raggedness)?

This is a real-world application, not a student assignment. Suppose we have some numbered boxes which are to be laid out, in order, from left to right, top to bottom, with no space between them, into ...
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### Trying to find all possible combinations

I am trying to find all the combination of options trades that make the highest profit. Each trade has a maximum profit and maximum loss. I have a list of maximum losses e.g. [5298, 1100, 500]. Each ...
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### Knapsack Problem with exact required item number constraint

How would we solve the knapsack problem if we now have to fix the number of items in the knapsack by a constant $L$? This is the same problem (max weight of $W$, every item have a value $v$ and weight ...
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### Working of the GHS algorithm

Can someone explain the working of the GHS algorithm using the graph given below. GHS is a distributed algorithm for finding the Minimum Spanning tree of a graph. The description of which can be found ...
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### Properties of roots of recurrence relations in the context of exponential algorithms in order to decrease the upper bound of the running time

The book "Exact Exponential Algorithms" by Fedor V. Fomin and Dieter Kratsch is an excellent book to start learning how to design exact exponential algorithms. In their second chapter, they introduce ...
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### Generate all combinations of a set/array with specific conditions

Apologies if this isn't posted in the right stack exchange, but I'm trying to come up with an algorithm that generates a set of sets ('set' as synonymous with 'array') with the following conditions: ...
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### Given a set of (x,y) coordinates, give the set of edges to draw a simple polygon

Let's say I give you the following array of points: (1,1) (1,3), (2,2), (4,1), (4,3) My (terrible) mspaint drawing of the shape that would be created by these looks like this: How, given an ...
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### rolling around running numbers

I'm numbering generated files with two digits 00-99 and I want to retain the last 50. The algorithm should tell me the number of the current file that I'm about to save and which of the previous files ...
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### Solving NP problems : analogy between the SAT problem and the shortest path problem

in this 2minute-long video https://www.youtube.com/watch?v=TJ49N6WvT8M (pulled from a free udacity course on algorithms/theoretical computer sciences), whose purpose is to show how a SAT problem can ...
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### Floyd's Cycle detection algorithm | Determining the starting point of cycle

I am seeking help understanding Floyd's cycle detection algorithm. I have gone through the explanation on wikipedia (http://en.wikipedia.org/wiki/Cycle_detection#Tortoise_and_hare) I can see how the ...
I want to generate a random partition of an $N\times N$ grid into $N$ connected groups having $N$ tiles each. How would I do this? Max grid size will be 10x10. Below is an example for a 5x5 grid.