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• Choice of programming language for learning data structures and algorithms

  - by bguiz

  Which programming language would you recommend to learn about data structures and algorithms in? Considering the follwing: Personal experience Language features (pointers, OO, etc) Suitability for learning DS & A concepts I ask because there are some books out there that are programming language-agnostic (written from a Mathematical perspective, and use pseudocode). If I learn from one of these I would like to work out the algorithms in a chosen language. Then, there are other books which introduce DS & A concepts with examples in a particular programming laguage - and I would follow these examples as well. Either way, I have to choose a language, and I would like to stick to one throughout. Which one best fits the bill.

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• Methodologies or algorithms for filling in missing data

  - by tbone

  I am dealing with datasets with missing data and need to be able to fill forward, backward, and gaps. So, for example, if I have data from Jan 1, 2000 to Dec 31, 2010, and some days are missing, when a user requests a timespan that begins before, ends after, or encompasses the missing data points, I need to "fill in" these missing values. Is there a proper term to refer to this concept of filling in data? Imputation is one term, don't know if it is "the" term for it though. I presume there are multiple algorithms & methodologies for filling in missing data (use last measured, using median/average/moving average, etc between 2 known numbers, etc. Anyone know the proper term for this problem, any online resources on this topic, or ideally links to open source implementations of some algorithms (C# preferably, but any language would be useful)

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• how to tackle this combinatorial algorithm problem

  - by Andrew Bullock

  I have N people who must each take T exams. Each exam takes "some" time, e.g. 30 min (no such thing as finishing early). Exams must be performed in front of an examiner. I need to schedule each person to take each exam in front of an examiner within an overall time period, using the minimum number of examiners for the minimum amount of time (i.e. no examiners idle) There are the following restrictions: No person can be in 2 places at once each person must take each exam once noone should be examined by the same examiner twice I realise that an optimal solution is probably NP-Complete, and that I'm probably best off using a genetic algorithm to obtain a best estimate (similar to this? http://stackoverflow.com/questions/184195/seating-plan-software-recommendations-does-such-a-beast-even-exist). I'm comfortable with how genetic algorithms work, what i'm struggling with is how to model the problem programatically such that i CAN manipulate the parameters genetically.. If each exam took the same amount of time, then i'd divide the time period up into these lengths, and simply create a matrix of time slots vs examiners and drop the candidates in. However because the times of each test are not necessarily the same, i'm a bit lost on how to approach this. currently im doing this: make a list of all "tests" which need to take place, between every candidate and exam start with as many examiners as there are tests repeatedly loop over all examiners, for each one: find an unscheduled test which is eligible for the examiner (based on the restrictions) continue until all tests that can be scheduled, are if there are any unscheduled tests, increment the number of examiners and start again. i'm looking for better suggestions on how to approach this, as it feels rather crude currently.

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• Bouncycastle encryption algorithms not provided

  - by David Read

  I'm trying to use BouncyCastle with android to implement ECDH and EL Gamal. I've added the bouncycastle jar file (bcprov-jdk16-144.jar) and written some code that works with my computers jvm however when I try and port it to my android application it throws: java.security.NoSuchAlgorithmException: KeyPairGenerator ECDH implementation not found A sample of the code is: Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider()); java.security.KeyPairGenerator keyGen = org.bouncycastle.jce.provider.asymmetric.ec.KeyPairGenerator.getInstance("ECDH", "BC"); ECGenParameterSpec ecSpec = new ECGenParameterSpec("prime192v1"); keyGen.initialize(ecSpec, SecureRandom.getInstance("SHA1PRNG")); KeyPair pair = keyGen.generateKeyPair(); PublicKey pubk = pair.getPublic(); PrivateKey prik = pair.getPrivate(); I then wrote a simple program to see what encryption algorithms are available and ran it on my android emulator and on my computers jvm the code was: Set<Provider.Service> rar = new org.bouncycastle.jce.provider.BouncyCastleProvider().getServices(); Iterator<Provider.Service> ir = rar.iterator(); while(ir.hasNext()) System.out.println(ir.next().getAlgorithm()); On android I do not get any of the EC algorithms while ran normally on my computer it's fine. I'm also getting the following two errors when compiling for a lot of the bouncy castle classes: 01-07 17:17:42.548: INFO/dalvikvm(1054): DexOpt: not resolving ambiguous class 'Lorg/bouncycastle/asn1/ASN1Encodable;' 01-07 17:17:42.548: DEBUG/dalvikvm(1054): DexOpt: not verifying 'Lorg/bouncycastle/asn1/ess/OtherSigningCertificate;': multiple definitions What am I doing wrong?

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• Suggestions of the easiest algorithms for some Graph operations

  - by Nazgulled

  Hi, The deadline for this project is closing in very quickly and I don't have much time to deal with what it's left. So, instead of looking for the best (and probably more complicated/time consuming) algorithms, I'm looking for the easiest algorithms to implement a few operations on a Graph structure. The operations I'll need to do is as follows: List all users in the graph network given a distance X List all users in the graph network given a distance X and the type of relation Calculate the shortest path between 2 users on the graph network given a type of relation Calculate the maximum distance between 2 users on the graph network Calculate the most distant connected users on the graph network A few notes about my Graph implementation: The edge node has 2 properties, one is of type char and another int. They represent the type of relation and weight, respectively. The Graph is implemented with linked lists, for both the vertices and edges. I mean, each vertex points to the next one and each vertex also points to the head of a different linked list, the edges for that specific vertex. What I know about what I need to do: I don't know if this is the easiest as I said above, but for the shortest path between 2 users, I believe the Dijkstra algorithm is what people seem to recommend pretty often so I think I'm going with that. I've been searching and searching and I'm finding it hard to implement this algorithm, does anyone know of any tutorial or something easy to understand so I can implement this algorithm myself? If possible, with C source code examples, it would help a lot. I see many examples with math notations but that just confuses me even more. Do you think it would help if I "converted" the graph to an adjacency matrix to represent the links weight and relation type? Would it be easier to perform the algorithm on that instead of the linked lists? I could easily implement a function to do that conversion when needed. I'm saying this because I got the feeling it would be easier after reading a couple of pages about the subject, but I could be wrong. I don't have any ideas about the other 4 operations, suggestions?

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• implementing cryptographic algorithms, specifically the key expansion part

  - by masseyc

  Hey, recently I picked up a copy of Applied Cryptography by Bruce Schneier and it's been a good read. I now understand how several algorithms outlined in the book work, and I'd like to start implementing a few of them in C. One thing that many of the algorithms have in common is dividing an x-bit key, into several smaller y-bit keys. For example, blowfish's key, X, is 64-bits, but you are required to break it up into two 32-bit halves; Xl and Xr. This is where I'm getting stuck. I'm fairly decent with C, but I'm not the strongest when it comes to bitwise operators and the like. After some help on IRC, I managed to come up with these two macros: #define splitup(a, b, c) {b = a >> 32; c = a & 0xffffffff; } #define combine(a, b, c) {a = (c << 32) | a;} Where a is 64 bits and b and c are 32 bits. However, the compiler warns me about the fact that I'm shifting a 32 bit variable by 32 bits. My questions are these: what's bad about shifting a 32-bit variable 32 bits? I'm guessing it's undefined, but these macros do seem to be working. Also, would you suggest I go about this another way? As I said, I'm fairly familiar with C, but bitwise operators and the like still give me a headache.

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• Aligning music notes using String matching algorithms or Dynamic Programming

  - by Dolphin

  Hi I need to compare 2 sets of musical pieces (i.e. a playing-taken in MIDI format-note details extracted and saved in a database table, against sheet music-taken into XML format). When evaluating playing against sheet music (i.e.note details-pitch, duration, rhythm), note alignment needs to be done - to identify missed/extra/incorrect/swapped notes that from the reference (sheet music) notes. I have like 1800-2500 notes in one piece approx (can even be more-with polyphonic, right now I'm doing for monophonic). So will I have to have all these into an array? Will it be memory overloading or stack overflow? There are string matching algorithms like KMP, Boyce-Moore. But note alignment can also be done through Dynamic Programming. How can I use Dynamic Programming to approach this? What are the available algorithms? Is it about approximate string matching? Which approach is much productive? String matching algos like Boyce-Moore, or dynamic programming? How can I assess which is more effective? Greatly appreciate any insight or suggestions Thanks in advance

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• Intelligent web features, algorithms (people you may follow, similar to you ...)

  - by hilal

  I have 3 main questions about the algorithms in intelligent web (web 2.0) Here the book I'm reading http://www.amazon.com/Algorithms-Intelligent-Web-Haralambos-Marmanis/dp/1933988665 and I want to learn the algorithms in deeper 1. People You may follow (Twitter) How can one determine the nearest result to my requests ? Data mining? which algorithms? 2. How you’re connected feature (Linkedin) Simply algorithm works like that. It draws the path between two nodes let say between Me and the other person is C. Me - A, B - A connections - C . It is not any brute force algorithms or any other like graph algorithms :) 3. Similar to you (Twitter, Facebook) This algorithms is similar to 1. Does it simply work the max(count) friend in common (facebook) or the max(count) follower in Twitter? or any other algorithms they implement? I think the second part is true because running the loop dict{count, person} for person in contacts: dict.add(count(common(person))) return dict(max) is a silly act in every refreshing page. 4. Did you mean (Google) I know that they may implement it with phonetic algorithm http://en.wikipedia.org/wiki/Phonetic_algorithm simply soundex http://en.wikipedia.org/wiki/Soundex and here is the Google VP of Engineering and CIO Douglas Merrill speak http://www.youtube.com/watch?v=syKY8CrHkck#t=22m03s What about first 3 questions? Any ideas are welcome ! Thanks

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• Choices in Architecture, Design, Algorithms, Data Structures for effective RDF Reasoning and Querying in a Big Data Environment [on hold]

  - by user2891213

  As part of my academic project I would like to know what choices in Architecture, Design, Algorithms, Data Structures do we need in order to provide effective and efficient RDF Reasoning and Querying in a Big Data Environment. Basically I want to get info regarding below points: What are the Systems and Software to get appropriate Architecture? What kind of API layer(s) would we need on top of the Big Data stores, to make this possible? The Indexing structures we will need. The appropriate Algorithms, and appropriate Algorithms for Query Planning across Big Data stores. The Performance Analysis and Cost Models we will need to justify the design decisions we have made along the way. Can anyone please provide pointers.. Thanks, David

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• Suggested GA operators for a TSP problem?

  - by Mark

  I'm building a genetic algorithm to tackle the traveling salesman problem. Unfortunately, I hit peaks that can sustain for over a thousand generations before mutating out of them and getting better results. What crossover and mutation operators generally do well in this case?

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• HLSL, Program pixel shader with different Texture2D downscaling algorithms

  - by Kaminari

  I'm trying to port some image interpolation algorithms into HLSL code, for now i got: float2 texSize; float scale; int method; sampler TextureSampler : register(s0); float4 PixelShader(float4 color : COLOR0, float2 texCoord : TEXCOORD0) : COLOR0 { float2 newTexSize = texSize * scale; float4 tex2; if(texCoord[0] * texSize[0] > newTexSize[0] || texCoord[1] * texSize[1] > newTexSize[1]) { tex2 = float4( 0, 0, 0, 0 ); } else { if (method == 0) { tex2 = tex2D(TextureSampler, float2(texCoord[0]/scale, texCoord[1]/scale)); } else { float2 step = float2(1/texSize[0], 1/texSize[1]); float4 px1 = tex2D(TextureSampler, float2(texCoord[0]/scale-step[0], texCoord[1]/scale-step[1])); float4 px2 = tex2D(TextureSampler, float2(texCoord[0]/scale , texCoord[1]/scale-step[1])); float4 px3 = tex2D(TextureSampler, float2(texCoord[0]/scale+step[0], texCoord[1]/scale-step[1])); float4 px4 = tex2D(TextureSampler, float2(texCoord[0]/scale-step[0], texCoord[1]/scale )); float4 px5 = tex2D(TextureSampler, float2(texCoord[0]/scale+step[0], texCoord[1]/scale )); float4 px6 = tex2D(TextureSampler, float2(texCoord[0]/scale-step[0], texCoord[1]/scale+step[1])); float4 px7 = tex2D(TextureSampler, float2(texCoord[0]/scale , texCoord[1]/scale+step[1])); float4 px8 = tex2D(TextureSampler, float2(texCoord[0]/scale+step[0], texCoord[1]/scale+step[1])); tex2 = (px1+px2+px3+px4+px5+px6+px7+px8)/8; tex2.a = 1; } } return tex2; } technique Resample { pass Pass1 { PixelShader = compile ps_2_0 PixelShader(); } } The problem is that programming pixel shader requires different approach because we don't have the control of current position, only the 'inner' part of actual loop through pixels. I've been googling for about whole day and found none open source library with scaling algoriths used in loop. Is there such library from wich i could port some methods? I found http://www.codeproject.com/KB/GDI-plus/imgresizoutperfgdiplus.aspx but I really don't understand His approach to the problem, and porting it will be a pain in the ... Wikipedia tells a matematic approach. So my question is: Where can I find easy-to-port graphic open source library wich includes simple scaling algorithms? Of course if such library even exists :)

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• String searching algorithms

  - by avd

  For the two string searching algorithms: KMP and suffix tree, which is preferred in which cases? Give some practical examples.

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• Are there any ball tracking algorithms/patterns around in game programming

  - by user214626

  Hello, I am a newbie to game programming,I would need the suggestions and help of the wonderful people around here. I have set of players, and a ball, the players can kick the ball around the ground (not yet a football game, neither a foosball game too ).Are there any algorithms/ patterns for addressing the problems with tracking the ball and taking decisions, Is that too much to ask.What I was looking at is something like a collision detection algorithm for the common problem of 2 objects interacting with one another.

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• STL algorithms and concurrent programming

  - by Andrew

  Hello everyone, Can any of STL algorithms/container operations like std::fill, std::transform be executed in parallel if I enable OpenMP for my compiler? I am working with MSVC 2008 at the moment. Or maybe there are other ways to make it concurrent? Thanks.

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• QR code (2D barcode) coding and decoding algorithms?

  - by Adam Davis

  Looking for free/opensource code or description of algorithms to code (simple) and decode (hard) the 2D barcode QR code. It doesn't seem like a trivial problem, but it's so popular in Japan that there must be something already available...

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• Algorithms or OO stuff or new technology

  - by Prashant

  I am trying to learn new stuff about jquery, html, asp .net mvc. I see two school of thoughts - Those who use oo concepts a lot and stress on more object oriented approach Those who rely heavily on algorithms and say a particular problem should take o(n) etc. I am not sure where to spend more time ? . Should I spend more time learning OO stuff or learn new stuff like jquery etc or learn travelling sales man algorithm etc ?

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• Searching, Sorting and Graph Algorithms questions

  - by user177883

  Is there a resource that i can find different variations of searching, sorting and graph algorithm questions ? I have studied CLRS and Algorithm Design by Kleinberg. and solved some set of questions. I have also, checked SO for algorithms questions. Curious, if there is a resource you would highly recommend. EDIT: There is also this free ebook with many questions, that i was able to solve some of them.

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• Algorithms for subgraph isomorphism detection

  - by Jack

  This a NP Complete problem. More info can be found here http://en.wikipedia.org/wiki/Subgraph_isomorphism_problem The most widely used algorithm is the one proposed by Ullman. Can someone please explain the algorithm to me. I read a paper by him and couldn't understand much. Also what other algorithms for this problem. I am working on an image processing project.

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• An extended Bezier Library or Algorithms of bezier operations

  - by Sorush Rabiee

  Hi, Is there a library of data structures and operations for quadratic bezier curves? I need to implement: bezier to bitmap converting with arbitrary quality optimizing bezier curves common operations like subtraction, extraction, rendering etc. languages: c,c++,.net,python Algorithms without implementation (pseudocode or etc) could be useful too. (especially optimization)

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• efficacy of register allocation algorithms!

  - by aksci

  i'm trying to do a research/project on register allocation using graph coloring where i am to test the efficiency of different optimizing register allocation algorithms in different scenarios. how do i start? what are the prerequisites and the grounds with which i can test them. what all algos can i use? thank you!

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• Analysis of algorithms (complexity)

  - by Yktula

  How are algorithms analyzed? What makes quicksort have an O(n^2) worst-case performance while merge sort has an O(n log(n)) worst-case performance?

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• software for sorting algorithms animation

  - by Dinesh

  I am planning on working on an interactive application that graphically animates the various sorting algorithms in action. Most of the examples of this kind on the web seems to be using java applets. I was wondering what other software/tools would be well suited to develop an application like this. It may or may not be web-based. Any help would be greatly appreciated. Thanks Dinesh

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• graph algorithms on GPU

  - by scatman

  the current GPU threads are somehow limited (memory limit, limit of data structures, no recursion...). do you think it would be feasible to implement a graph theory problem on GPU. for example vertex cover? dominating set? independent set? max clique?.... is it also feasible to have branch-and-bound algorithms on GPUs? Recursive backtracking?

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• Balancing heuristics (for timetable problem)

  - by genesiss

  I'm writing a genetic algorithm for generating timetables. At the moment I'm using these two heuristics: Number of holes between lectures in one day (related) (less holes - bigger score) Each hour has some value, so for each timetable I sum values for hours when lectures are on. (lectures at more appropriate hours - bigger score) I want to balance these two heuristics, so the algorithm wouldn't favor neither one. What would be the best way to achieve this?

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• Travelling Salesman Problem Constraint Representation

  - by alex25

  Hey! I read a couple of articles and sample code about how to solve TSP with Genetic Algorithms and Ant Colony Optimization etc. But everything I found didn't include time (window) constraints, eg. "I have to be at customer x before 12am)" and assumed symmetry. Can somebody point me into the direction of some sample code or articles that explain how I can add constraints to TSP and how I can represent those in code. Thanks!

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