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.

learn more… | top users | synonyms (1)

0
votes
2answers
134 views

finding patterns into logs

I am trying to put together a way to figure out if incidents occurred based on log content. Typically, on log (or db table) would contain a list of transactions composed as follow: {Timestamp} ...
2
votes
4answers
2k views

Complexity in nested loops

Foreword: In this post, I will make the common confusion between O(n) and Theta(n) as complexity notations. I will write pseudo-code to talk about algorithms, using whatever notation I find to my ...
4
votes
3answers
459 views

Optimal “if-else” tree algorithm to minimize duplicate code

I'm having trouble formulating this problem as an algorithm: I have a set of conditionals (combined with &&) and operations, for example: if (A && B) execute C else if (D ...
-1
votes
1answer
326 views

Will interns and entry level positions care more about algorithms or projects/experience [closed]

I am 3 months into learning java, read head first java and made 4 things on my github + many small things. I also started learning android this month, but now am tossing and turning not knowing my ...
2
votes
1answer
242 views

Fully Stable, In-Place Unique Algorithm in O(n)

Is there an algorithm that, given a sorted array, swaps all the first unique elements to the beginning of the array and the duplicates to the end, while remaining stable for both the unique subarray ...
7
votes
3answers
373 views

Algorithm to use for shop floor layout?

I ran into a classroom problem yesterday (business oriented class, not computer science) and I found it interesting from an algorithmic perspective. The problem goes something like this: Assume there ...
7
votes
5answers
5k views

Most Efficient Cache Replacement Algorithm [closed]

Wikipedia lists 11 cache replacement algorithms. Assuming I know almost nothing about the application I'm going to develop, what should I use as a "default" cache replacement algorithm? If I recall ...
2
votes
1answer
90 views

What HTTP status codes need to be checked for this network task to perform smoothly?

My office department logs in to the ISP Server through a keep-alive-browser login page. This, for better performance, is encapsulated in to a small python script. This is what it does (Pseudo code) ...
0
votes
0answers
43 views

Designing online exam [duplicate]

I need to design an online exam server for an exam like GRE in which question difficulty increases if you answer correctly and decreases if you answer wrong. Questions are multiple choice ...
0
votes
1answer
231 views

Designing online exam

I need to design an online exam server for an exam like GRE in which question difficulty increases if you answer correctly and decreases if you answer wrong. Questions are multiple choice ...
3
votes
1answer
92 views

Algorithm that determines relevant attributes in ordered list

Suppose I have a list of objects sorted by a person based on that person's subjective taste. Let's assume that this person is being somewhat consistent in their sorting and that there are quantifiable ...
3
votes
2answers
383 views

Algorithm to find times when resources are available

I'm writing a semi-automatic scheduling application. Given some existing bookings and some resource requirements, it needs to find the times at which a new event can be scheduled. A human user will ...
12
votes
1answer
755 views

How did Strassen come up with his matrix multiplication method?

The famous Strassen's matrix multiplication algorithm is a real treat for us, as it reduces the time complexity from the traditional O(n^3) to O(n^2.8). But of all the resources I have gone through, ...
14
votes
4answers
3k views

Is this XOR value swap algorithm still in use or useful

When I first started working a mainframe assembler programmer showed me how they swap to values without using the traditional algorithm of: a = 0xBABE b = 0xFADE temp = a a = b b = temp What they ...
15
votes
2answers
825 views

Algorithm for fast tag search

The problem is the following. There's a set of simple entities E, each one having a set of tags T attached. Each entity might have an arbitrary number of tags. Total number of entities is near 100 ...
2
votes
1answer
108 views

How to know, with good performance, which areas a certain point is in? [duplicate]

I'm interested in build a prototype that needs this sort of thing: Point A (xa, ya) with a radius of 500 meters. Point B (xb, yb) with a radius of 700 meters. Point C (xc, yc) with a radius of 1200 ...
2
votes
2answers
266 views

Graph traversal and filtering in indoor navigation and path finding

Which of the following options take less processing time/is less expensive in a graph traversal algorithm for a (indoor)navigation system? a) To produce all possible paths between start and ...
0
votes
1answer
144 views

fill containers with blocks of different sizes to have containers of “similar” sizes [closed]

I have a sorted list of blocks L that I want to put in 4 containers C, the containers have a size limit S. I want to have similar containers height, by similar I mean the size variance should be as ...
6
votes
3answers
331 views

Unit (regression) testing scientific algorithms given floating point behavior

I have been working on a project and running into a very difficult problem. The problem can be stated simply as how to unit-test numerical algorithms. However if you just took this simple statement ...
2
votes
1answer
160 views

Cohen–Sutherland algorithm

I was reading Cohen–Sutherland algorithm on Wikipedia and I am confused in these two parts, int ComputeOutCode(double x, double y) { ... if (x < xmin) code |= LEFT; else if (x ...
12
votes
4answers
1k views

How do you identify a problem as being suitable for dynamic programming?

I have been reading up on dynamic programming lately. Would like to hear from someone who started from scratch and now is pretty good at identifying and solving DP problems. I am struggling in ...
9
votes
1answer
4k views

Am I right about the differences between Floyd-Warshall, Dijkstra's and Bellman-Ford algorithms?

I've been studying the three and I'm stating my inferences from them below. Could someone tell me if I have understood them accurately enough or not? Thank you. Dijkstra's algorithm is used only ...
7
votes
3answers
2k views

Is there a known algorithm for scheduling tournament matchups?

Just wondering if there is a tournament scheduling algorithm already out there that I could use or even adapt slightly. Here are my requirements: A variable number of opponents belonging to a ...
1
vote
1answer
536 views

When interviewing programmers, are algorithm problem solving skills relevant for a job were solving such algoritm problems isn't normally needed? [closed]

Software created for some business domains don't require heavy use of algorithm problem solving skills on the job from the programmers working there. For example, a JEE developer might most of the ...
2
votes
3answers
2k views

Sorting an array of numbers with decimal places

Suppose I have an array of float values in the following format: { 1.34, 1.15, 1.1, 1.2, 1.26, 1.10, 1.20, 1.17 } Suppose they have been provided by user input (or some other mechanism), where the ...
5
votes
4answers
398 views

How are algorithms developed? [closed]

I'm impressed with the efficiency of some algorithms and I noticed the way the problem is solved can be and/or appear really unintuitive. It may sound dumb, but I would like to know: How do the ...
0
votes
0answers
124 views

How to algorithmically add notes to an existing midi file relative to positions of existing notes in python

I have a midi file that I'd like to algorithmically add notes to relative to other notes that already exist in the midi file using python, or if it's easier using a different language I'm open to that ...
0
votes
3answers
816 views

Algorithm for recursive evaluation of postfix expressions

I'm reading Sedgewick's book on algorithms in C and I'm looking for an algorithm to evaluate postfix expressions (addition and multiplication only) without using a stack. I tried to implement one but ...
2
votes
1answer
125 views

Comparing strings against a pool of words

I am creating an app where the user enters 8 characters. After he enters the string I have to see if it is an eight letter word. If not, check if contains a seven letter word etc. I am checking ...
3
votes
0answers
187 views

Help/suggestions for Parallel assembly line scheduling (Dynamic programming)

I am working on a problem similar to the assembly line scheduling by dynamic programming.The issue is that unlike the classic problem where we have predefined stations now I only have information ...
3
votes
1answer
2k views

Database design/relationship for threading messages

What's the database design or business logic for creating an app for messaging between users? I am having difficulties with choosing how to approach the relationship between each Conversation of User ...
0
votes
1answer
294 views

Can someone help me in creating a dynamic programming solution to this problem?

I have some function names which are assigned to some nodes. I have to decide which functions to move to other nodes to increase speed. Why do I have to move the functions to other nodes? If ...
1
vote
1answer
133 views

Search Substring in String collection

I have a big collection of strings a[1], …, a[N] where N is about several millions. I am provided a string m and I need to iterate over all the strings a[i] that contain m. In other words, I need to ...
0
votes
1answer
114 views

Better way to create samples

I've done this piece of code for creating bernulli samples, but I think that it is a so heavy algorithm because every time I call this recursive function I create a new vector that is passed to it. Is ...
4
votes
3answers
807 views

Round Table - Minimum Cost Algorithm

Problem Link - http://www.iarcs.org.in/zco2013/index.php/problems/ROUNDTABLE It's dinner time in Castle Camelot, and the fearsome Knights of the Round Table are clamouring for dessert. You, the ...
2
votes
3answers
920 views

Evaluate all pair combinations in an array for a condition in n log n time complexity

Task - Consider an array of n elements. Count the number of pairs that satisfy condition X (sum of the two elements < an arbitrary number, k) . The basic approach I could think of would be O(n^2), ...
0
votes
0answers
67 views

Optimal group room division algorithm with weights

I hope someone can help me with this, as I'm thoroughly stuck. I'm working with a group at my university, on a first semester research report that should end up as a finished program, solving the ...
2
votes
3answers
210 views

Algorithm to calculate estimated future usage of a defined value

I am looking for the name of a computer algorithm. I'm fairly sure that one should exist which will help me, but I can't for the life of me figure out what to search for. If you have implementations ...
22
votes
3answers
3k views

What are the data structures behind a spreadsheet?

I would like to understand how a spreadsheet (a group of named or otherwise identified cells containing values or formulas referencing other cells) is solved. I have tried looking at existing ...
1
vote
1answer
140 views

How to calculate the worst-case runtime of this search-algorithm

I've written a special indexOf function for a list of unsorted unique values. I can search for one or multiple (unsorted) values, passed as array/list, and the function will return me an array/list ...
4
votes
3answers
112 views

Approach to algorithm for assignment of resources

We have a requirement to be able to match people with locations based on availability and certain conditions. Let's say I have a group of people each with 3 types of things they may need to park. A ...
8
votes
3answers
631 views

Is there a general method to evaluate the optimality of an optimization algorithm?

is there a general method to evaluate the optimality of an optimization algorithm, for example an algorithm solving an otherwise NP-hard or NP-complete problem? The only method I came up so far is ...
7
votes
4answers
482 views

Fastest way to check if two square 2D arrays are rotationally and reflectively distinct

The best idea I have so far is to rotate first array by {0, 90, 180, 270} degrees and reflect it horizontally or/and vertically. We basically get 16 variations [1] of first array and compare them with ...
2
votes
1answer
60 views

computing whether service level times are met

For a ticket reporting tool, I want to compute whether certain service level times (slt) are met. That is (a bit simplified): Was the timespan between opening and closing of the ticket within a ...
29
votes
5answers
5k views

Programming interview question on Trees

I was asked this interview question at a top internet website company recently. Certain empty glasses of water are arranged in the following order When you pour liquid into the 1st glass if ...
0
votes
1answer
52 views

Layered Manufacturing Contour Generation

I am currently working on software for layered manufacturing (3D printing), and have come to a point where I no longer know what to do. I am at the stage where I must take a bunch of lines, and order ...
2
votes
1answer
347 views

Shuffling algorithm with no “self-mapping”?

To randomly shuffle an array, with no bias towards any particular permutation, there is the Knuth Fischer-Yeats algorithm. In Python: #!/usr/bin/env python import sys from random import randrange ...
13
votes
3answers
602 views

Searching integer sequences

I have a fairly complex search problem that I've managed to reduce to the following description. I've been googling but haven't been able to find an algorithm that seems to fit my problem cleanly. In ...
2
votes
2answers
675 views

Ring of numbers where adjacent entries sum up to a prime

Given a number n, find a permutation of the numbers 1...n such that all adjacent entries sum up to primes. If such a permutation does not exist, throw an error. Is there a purely-functional way to do ...
1
vote
2answers
361 views

Making an algorithm more efficient

I have a question about the efficiency of an algorithm: You have a list of x,y points Now I want to get all the points that are up to 5 units away from a reference x,y point How do you calculate it ...