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.

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Is MapReduce anything more than just an application of divide and conquer?

Dividing a problem to smaller ones until the individual problems can be solved independently and then combining them to answer the original question is known as the divide and conquer algorithm design ...
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Calendar/Planning algorithm

I'm facing a problem I'm not sure how to approach. I have to generate a calendar for employees, each of them having specific work constraints (some personal, some common) What I'm working with : I ...
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Which algorithms and data structures should a developer absolutely know? [closed]

I want to be a successful enterprise Java developer. With what algorithms and data structures should I be well versed? What books would you recommend to me? To be a successful Java developer, do I ...
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Do algorithms depend on computer architectures?

I read somewhere (forgot which book it is) that algorithms are independent of computer architectures. Some even say algorithms are themselves computation (machines?)? On the other hand, books on ...
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How do I express subtle relationships in my data?

"A" is related to "B" and "C". How do I show that "B" and "C" might, by this context, be related as well? Example: Here are a few headlines about a recent Broadway play: David Mamet's Glengarry ...
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What modern alternatives to Numerical Recipes exist? [closed]

In the past, the Numerical Recipes book was considered the gold standard reference for numerical algorithms. The earliest Fortran Edition was followed by editions in C and C++ and others, bringing it ...
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3d Packing algorithm for item's shipping

I've received a task to build a shipping estimative that suggests the best accomodation of goods on as few boxes as possible: There is a finite set of known retangular box sizes There are many ...
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When speaking, how can I say that the time complexity order of an algorithm is O(N log N)?

What term can I use to describe something with O(N log N) complexity? For example: O(1): Constant O(log N): Logarithmic O(N): Linear O(N log N): ?????? O(N2): Quadratic O(N3): Cubic
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What are good mathematical formulas to know for programming? [closed]

What are some somewhat common math formulas you learned that helped you write better algorithms and become a better programmer? Example: I learned about the ecludian distance formula: sqrt((x1-x2)^2+(...
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Is it essential to learn algorithms to be a real programmer? [closed]

I'm a PHP programmer, and until now I have not needed to learn algorithms... Now I'm start learning Python (a real programming language), because I need to use matplotlib. Does it make sense to start ...
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How to write a command interpreter/parser?

Problem: Run commands in the form of a string. command example: /user/files/ list all; equivalent to: /user/files/ ls -la; another one: post tw fb "HOW DO YOU STOP THE TICKLE MONSTER?;" ...
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What algorithms are there for picking colors for plot lines on graphs?

I'm interested in what algorithms or rules I can programmatically implement to generate RGB or HSV colors for plotlines to keep them visually distinct from the neighbors. I know that in professional ...
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In pseudo code what does := mean?

The section entitled Algorithmic Implementation has the following code: // Return RC low-pass filter output samples, given input samples, // time interval dt, and time constant RC function ...
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Advantage in being the first to copyleft a new algorithm? [closed]

Say I have created a new (DSP) algorithm. Will I have some advantage if I open source the algorithm under copyleft licence (GPL etc.)? From what I know about licensing this should lock people out from ...
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Java and .NET: Why different sorting algorithms are used by default?

Just wondering why Java and .NET Framework uses different sorting algorithm by default. In Java Array.Sort() uses Merge Sort algorithm by default and as Wikipedia.com says: In Java, the Arrays....
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What class of problem is this, and what math do I need to know to solve it?

Mushroom cultivation requires fairly precise chemical composition of substrate (a.k.a. growing medium). Let's pretend we're growing shitakes and that this is the required composition of their ...
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How to turn truth table into smallest possible if / else block

How can I take a truth table and turn it into a compacted if block? For instance, let's say I have this truth table where A and B are conditions and x, y and z are possible actions: A B | x y z -----...
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Why do most languages provide a min-heap instead of a max-heap implementation?

I just noticed something and I wonder if there is any reason for that. Except for C++ (std::priority_queue is a max heap), I don't know any other language that offers a max heap. Python's heapq ...
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Algorithm for calculating a bullet path to a target with max. 2 ricochets

Sorry for the poor title but I didn't have a better way to phrase it... So there's this amazing game by Nintendo (yes!) on Wii called WiiPlay. There're 9 minigames in it, and my favorite one is ...
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Visiting points on a number line while minimizing a cost not related to distance

I need some help on this ACM ICPC problem. My current idea is to model this as a shortest path problem, which is described under the problem statement. Problem There are N = 1000 nuclear waste ...
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Algorithms: How do I sum O(n) and O(nlog(n)) together?

I have the follow algorithm which finds duplicates and removes them: public static int numDuplicatesB(int[] arr) { Sort.mergesort(arr); int numDups = 0; for (int i = 1; i < arr.length; ...
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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 ...
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How to quickly search through a very large list of strings / records on a database

I have the following problem: I have a database containing more than 2 million records. Each record has a string field X and I want to display a list of records for which field X contains a certain ...
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How would you implement Google Search? [closed]

Supposed you were asked in an interview "How would you implement Google Search?" How would you answer such a question? There might be resources out there that explain how some pieces in Google are ...
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Efficient graph clustering algorithm

I'm looking for an efficient algorithm to find clusters on a large graph (It has approximately 5000 vertices and 10000 edges). So far I am using the Girvan–Newman algorithm implemented in the JUNG ...
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Is this a Proper “Rule” for Identifying the “Big O” Notation of an Algorithm?

I've been learning more about Big O Notation and how to calculate it based on how an algorithm is written. I came across an interesting set of "rules" for calculating an algorithms Big O notation and ...
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Strategy/algorithm to divide fair teams based on history

We are a group of people playing floorball together on a regular basis. Every session starts with the daunting task of dividing teams... So what would be better than an application to pick teams ...
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What algorithms can I use to detect if articles or posts are duplicates?

I'm trying to detect if an article or forum post is a duplicate entry within the database. I've given this some thought, coming to the conclusion that someone who duplicate content will do so using ...
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Is having trouble with data structures common for beginners? [closed]

I'm taking my second course on Java. We are getting into data structures. I have done an assignment on a linked list, and now a stack. I had a hard time with the linked list. The stack gave me a ...
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Preferring Python over C for Algorithmic Programming

I've been studying a bit of algorithms and have been looking at sites like SPOJ.pl TopCoder etc. I've seen that programmers prefer C or C++ usually for most algorithmic programming contests. Now I'...
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Difference between a pseudo code and algorithm?

Technically, Is there a difference between these two words or can we use them interchangeably? Both of them more or less describe the logical sequence of steps that follow in solving a problem. ain't ...
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I know JavaScript really well, but i bomb coding interviews [closed]

So I'm currently on a hunt for a new position as a Front-End Developer. I know JavaScript very well and can wax poetically about Closures, Currying, Prototypal Inheritance, Design Patterns, App ...
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Why isn't Radix Sort used more often?

It's stable and has a time complexity of O(n). It should be faster than algorithms like Quicksort and Mergesort, yet I hardly ever see it used.
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Which string search algorithm is actually the fastest?

I have been stuck for some time on which is the fastest string search algorithm, heard many opinions, but in the end I'm not sure. I have heard some people saying that the fastest algorithm is Boyer-...
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How to find hard to misspell given names?

Here is a question that I believe could be solved with some data mining and a sophisticated algorithm, but I don't quite know how. Any pointers as to what data sources to use and what algorithm to ...
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Conflict resolution for two-way sync

How do you manage two-way synchronization between a 'main' database server and many 'secondary' servers, in particular conflict resolution, assuming a connection is not always available? For example, ...
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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 ...
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Is it possible to write a generalized string reverse function that works for all localisations and string types?

I was just watching the Jon Skeet (with Tony the Pony) presentation from Dev-Days. Although "write a string reverse function" is coding interview 101 - I'm not sure that it's actually possible to ...
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When to prefer a generalized solution over solving specific cases

In programming we're often faced with a choice: cover each conceivable use case individually, or solve the general problem: Its obvious that solving the immediate problem is faster, however ...
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TDD and complete test coverage where exponential test cases are needed

I am working on a list comparator to assist sorting an unordered list of search results per very specific requirements from our client. The requirements call for a ranked relevance algorithm with the ...
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Is there a subset of programs that avoid the halting problem

I was just reading another explanation of the halting problem, and it got me thinking all the problems I've seen that are given as examples involve infinite sequences. But I never use infinite ...
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Are Constant Time and Amortized Constant Time effectively considered equivalent?

I need to write a RandomQueue that allows for appends and random removal in Constant Time ( O(1) ). My first thought was to back it with some kind of Array (I chose an ArrayList), since arrays have ...
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What is a helper? Is it a design pattern? Is it an algorithm?

Maybe a little tongue-in-cheek, but as I can't find this answer anywhere through Google, so to ensure Programmers Stackexchange has the answer: What is a helper? I have seen the name being used ...
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NP complete or NP hard problems in real life

Does anybody have real life examples where they regularly solve NP complete or NP hard problems (by heuristics, or chasing a suboptimal solution or whatever) in their job? I know they occur in ...
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How does a garbage collector prevent the whole memory from being scanned on every collect?

Some (at least Mono's and .NET's) garbage collectors have a short term memory area which they scan often, and a secondary memory area which they scan less often. Mono calls this a nursery. To find ...
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Determining if an Algorithm is O (log n)

I'm refreshing my CS Theory, and I want to know how to identify that an algorithm O (log n) complexity. Specifically, is there an easy way to identify it? I know with O(n), you usually have a single ...
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Algorithm for Learning development [closed]

This is a fairly general question. I know a bit of Perl and Python and I am looking to learn programming in more depth so that once I get the hang of it I can start developing applications and then ...
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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 ...