# Tagged Questions

In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning.

216 views

### My algorithm is too slow

Reposted from Stack Overflow - I think this is a more appropriate place to ask the question. I have an algorithm that for an integer x and a starting integer i such that 1 < i < x the next ...
273 views

### What should I call this utility function? Is something like it commonly used?

Suppose you want to combine some arrays of objects that have similar properties: var people = [{name: 'Jack', age: 10}, {name: 'Jill', age: 12}] var items = [{owner: 'Jack', name: 'pail'}, {owner: '...
47 views

### Filtering algorithm for word game

Suppose you have a number of anagrams for the same letters, for example: alerting altering integral relating triangle Suppose you have a game where you must find all the anagrams, by placing letters ...
144 views

I have a problem dealing with word ladders. The problem is: given two words and a dictionary file, find the shortest word ladder between the two words. So if given the words cat and pot: cat -> ...
134 views

### Algorithm to create all unique sets of the alphabet using arbitrary group sizes

I'm looking for an algorithm to help me out with a combination of combinations problem. I have generated two lists of combinations of letters: (26 choose 6) & (26 choose 5) My goal is to be able ...
30 views

### How would I identify a gap in a set of curve data, and get its value?

I have a set of 2-D data (x,y) and it produces a set of curves, and sometimes the set of curves do not overlap, and there is a distinct separation between the groups of curves, how would I identify ...
78 views

### Ordering 'Tasks' for execution based on their dependencies

Let's say I have a set of Tasks that they have dependencies. These tasks are not in order, but the execution of tasks should be in the proper order. Each task has two properties: Before and After. ...
125 views

### Modelling a complex schedule of work

I've got a real-world problem that I'm trying to represent and automate. I've simplified and abstracted it down to the following: There are n places of work (P1, P2, ..., Pn). Each place, Pn has a ...
218 views

### Fuzzy algorithm for grouping data

I have data that indicates which topics each student has got right/wrong in an assessment.: | Student | Topic 1 | Topic 2 | Topic 3 | Topic 4 | Topic 5 | ... (perhaps 30 topics) | 1 | T | ...
159 views

### Binary Search O(log(n)) or O(n)

I see where most readings online derive that the Big-Oh notation of a Binary Search is O(log(n)), but doesn't this assume a balanced tree? What if the tree is completely unbalanced (i.e. similar to a ...
58 views

### Implementing an algorithm for parallel task scheduling

Problem Given a set of applications "A[]" with execution cost "Ex" ,Arrival Time "t", Resource requirements "R" and the system having free resources "Fr", calculate the finishing time of all of the ...
80 views

### Clairvoyance in caching - optimal strategies?

This question relates to the question here, but I'll generalise it so that you can answer effectively without reading all of that. Context: Imagine you had a large set of data greater than your ...
56 views

### Place X items in N matrices without repeat column and row

I have N matrices (n × m) and items to place in each one (n · m). The same items are repeated randomly for each matrix. When one item is placed in (i, j), for the following matrices the ...
73 views

### Caching in '3D' - data-structures and octree recursion - hrrm!

The Situation: I have 68GB of data that is conceptually realized as a 3D matrix of 8-bit values with dimension 4096*4096*4096. I need to access multiple sections of this data for processing in a ...
529 views

### What is Big-O notation for purely functional languages?

Is it still relevant? Instead of var result = new List<int>(); for (var i = 0; i < prev.Count; ++i) { result.Add(prev[i] * 2); } where the result.Add, prev[i], and * 2 instructions ...
61 views

### Algorithm and time-complexity of creating a sports schedule

With the NFL schedule being released last night, I started thinking. How would one automate the process of creating a schedule for a league such as the NFL? Even if we ignore all the challenges of a ...
250 views

### Algorithm to determine the fastest route passing in all points

Given a starting point A and an end point E, I need an algorithm to determine the minimum transit route in a city that passes through all points (A, B, C, D, E) and is the fastest possible. I know I ...
268 views

### Best compression algorithm for timelapse photos

I have a folder containing about 9,000 JPEG photos (about 30Gb), which I want to archive with some sort of compression. I understand that compressing JPEGs is not normally very effective, but these ...
99 views

### Calculating variable distances

I'm attempting to write an algorithm that calculates the distance between vertebrae. The text parser already works perfectly in picking out vertebral references (cervical 6, c-6, c6, c six, cervical ...
92 views

### Most efficient way to keep count of objects in State X without constantly counting

The application I work on manages hundreds of thousands of records each in a different state in their lifecycle. A large requirement is to have a nearly accurate count of these objects in each state ...
192 views

### Sudoku Solver BackTracking vs Simulated Annealing

Before you read any further, assume you know what sudoku game and how to go about solving it. So I have created a sudoku solver with brute-force: The algorithm goes as calculate(through an simple ...
39 views

### Algorithm for rate-limiting uploads with 3 files max

I want to limit file upload frequency to our webservice to prevent denial-of-service (directed at the server) - specifically, temporary folders filling up with fake uploads. This could be the user ...
75 views

### Algorithm for implementing QOS in my proxy

Here's the situation: I'm making a proxy (for the moment running on my laptop) which deals with HTTP(S) requests from incoming clients (for the moment only one client, i.e. my Chrome browser on my ...
139 views

### Data structure for determining intersection between line and polygon in 3D

I have a collection of non-self-overlapping simple polygons P. In actuality, they are 2D triangles in 3D-space. I'm looking for a data structure which, given a line L, has a relatively fast lookup ...
72 views

### Matrix multiplication range queries

I have a huge list of matrix i.e A = {M0, M1, M2 .. Mn}. I have a task to find the product of all the matrices in a given range {x,y} i.e Mx * Mx+1 * Mx+2 ... * My. I would like to know if there is ...
24 views

### Create unique buckets for stream of entities based on constraints on the entity attributes

I have stream (magnitude 10s of millions) of entities, say Item which is modeled as below: class Item { String id; Double price; Double profitPercentage; Country originCountry; Country ...
153 views

### Complexity of recursive calls

my brain is a little stuck as I am trying to compile an example for my blog. I am presenting an algorithm that draws a number from an array, adds it to a sum and calls itself recursively. func solve(...
144 views

### Check if list has a list of values

I have been trying to figure out an efficient algorithm that can check if a list of values contains a list of values. Both lists are sorted in ascending order. For example: Check if var ...
62 views

### Mapping match-up combinations into an integer

First of all, I want to say I wasn't sure if I should post this here or in math.stackexchange but I think the question is too programming-related to belong to the latter community. Definetly not a SO ...
77 views

### Find largest subset where two elements share a property

I have a set of numbers S and I want to find the largest subset S' such that for any two elements x,y in S' property(x, y) == True in_relation(x,y) == True. How could I find it? Bruteforcing is an ...
44 views

### Why use last column of Burrows-Wheeler-Transform

The Burrows-Wheeler-Transform takes a string with length n, creates a matrix with n rows by shifting this string one position to the left for each row. Then the rows are sorted by the first column in ...
61 views

### How to solve min cost max flow program with brute force

I have a use case where I need to solve min cost max flow problem for nodes < 5. Implementing Cycle canceling or some other min cost max flow problem seems like a over kill for this, is there some ...
173 views

### How to implement k-means algorithm on RGB Images?

I want to apply the k-means algorithm on an RGB image data-set. I don't know how to proceed. You can mention basic step by step flow to proceed. I do know basics of Image Processing & OpenCV.
55 views

### Are there any generic algorithims or Python functions to help find the longest item in a JSON document?

I am trying to log a JSON error message to Google's Cloud Logging platform. Unfortunately, the maximum size message you can log is 8000 bytes and some of the JSON documents I want to log are larger ...
323 views

### One font OCR for meme images

I'm coding an Optical Character Recognition specifically for the Internet meme images. This is a school project and it should be coded in C. I'm currently having trouble with the method/algorithms I ...
62 views

### How to represent complex permissions system in single hash or set of characters?

Eve Online, a game I used to play, had an interesting "permissions" system for account interactions with other apps. The permissions encompassed dozens of individual permissions, each under a ...
95 views

### Unable to Solve Dynamic Programming

I had an assignment on dynamic programming due last night, but I had to turn it in unfinished because i could not understand how to solve the last problem: The state wants to monitor traffic on a ...
138 views

### Which 3D algorithms does Windows 10's “3D Builder” application use?

Windows 10 ships with "3D Builder", a Universal App that contains utility functions to prepare STL, OBJ, 3DS, and other files that represent geometries for 3D printing. The utility looks like this: ...
143 views

### Best two-way compression algorithm for 32-bit numbers

I need to compress an id for marketing campaigns. The current campaign id is 32-bit integer but obviously this is too long for a customer to type by hand. I would like to compress this to minimum ...
148 views

### How do I generate multiple hashes that can be resolved to a single value?

I need multiple "random" URLs that just mask the original URL, i.e.: /ABC /CBA /CAB All resolve to /6 I came up with matching a letter to a number and then you can sum them to the single value. A ...
110 views

### tiling algorithm for maximum size of equal-sized tiles

I'm trying to fit an arbitrary number of HD videos on screen so that they all have equal size, maximizing the size of the videos, with no scrollbars appearing. Given N number of tiles of equal ...
119 views

### Algorithm to find span intersections in a sorted set

I have a set of items strictly ordered on time. Each item can either be single (no Next, no Previous) or part of a span (with either 1 or 2 further endpoints). For example in the picture A is part ...
2k views

### Is there any good search algorithm for a single character?

I know several basic string-matching algorithms such as KMP or Boyer-Moore, but all of those analyze the pattern before searching.However, if one has a single character, there is not much to analyze. ...
156 views

### How to find complexity of T(n) = 8T(n/2)+n^2.93(log n)^93?

I believe we have to use a variant of master theorem...can someone suggest me how to find complexity of such equation which doesn't directly fit into Masters theorem.
39 views

### Partition edges into areas

If I have a series of edges that branch and curve, such as in a road network, is there an algorithm that will identify the areas (defined by sequence of geographic points) defined between those lines? ...
239 views

### Dynamic Programming - Largest arrangement of bookcases

I'm trying to solve a problem, so I'm not looking for code, but for similar algorithms so I can solve it myself. I am given n bookcases each with a size amount of books inside. I am to move some of ...
169 views

### Algorithm to generate all sets of m points in n x n x n cubic lattice which are unique under symmetry

I am implementing an algorithm which is going to be quite computationally complex, and want to try to make sure I'm not doing unnecessary work. There is an n x n x n cubic lattice, e.g. if n=2 this ...
133 views

### Design for autocompleting words in search engine?

I'm trying to implement an autocomplete feature for a search engine. I have a database of words(stemmed) that occur in the documents that I have for users to search. What I am thinking of doing is: ...