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• GSM Cell Towers Location & Triangulation Algorithm (Similar to OpenCellID / Skyhook / Google's MyLocation)

  - by ranabra

  Hi all, assuming I have a Fingerprint DB of Cell towers. The data (including Long. & Lat. CellID, signal strength, etc) is achieved by 'wardriving', similar to OpenCellID.org. I would like to be able to get the location of the client mobile phone without GPS (similar to OpenCellID / Skyhook Wireless/ Google's 'MyLocation'), which sends me info on the Cell towers it "sees" at the moment: the Cell tower connected to, and another 6 neighboring cell towers (assuming GSM). I have read and Googled it for a long time and came across several effective theories, such as using SQL 2008 Spatial capabilities, or using an euclidean algorithm, or Markov Model. However, I am lacking a practical solution, preferably in C# or using SQL 2008 :) The location calculation will be done on the server and not on the client mobile phone. the phone's single job is to send via HTTP/GPRS, the tower it's connected to and other neighboring cell towers. Any input is appreciated, I have read so much and so far haven't really advanced much. Thanx

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• Reducing a set of non-unique elements via transformations

  - by Andrey Fedorov

  I have: 1) a "starting set" of not-necessarily-unique elements, e.x. { x, y, z, z }, 2) a set of transformations, e.x. (x,z) = y, (z,z) = z, x = z, y = x, and 3) a "target set" that I am trying to get by applying transformations to the starting set, e.x. { z }. I'd like to find an algorithm to generate the (possibly infinite) possible applications of the transformations to the starting set that result in the target set. For example: { x, y, z, z }, y => x { x, x, z, z }, x => z { z, x, z, z }, x => z { z, z, z, z }, (z, z) => z { z, z, z }, (z, z) => z { z, z }, (z, z) => z { z } This sounds like something that's probably an existing (named) problem, but I don't recognize it. Can anyone help me track it down, or suggest further reading on something similar?

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• Javascript algorithm to find elements in array that are not in another array

  - by Tauren

  I'm looking for a good algorithm to get all the elements in one array that are not elements in another array. So given these arrays: var x = ["a","b","c","t"]; var ?????????y = [???????"d","a","t","e","g"]; I want to end up with this array: var z = ["d","e","g"]; I'm using jquery, so I can take advantage of $.each() and $.inArray(). Here's the solution I've come up with, but it seems like there should be a better way. // goal is to get rid of values in y if they exist in x var x = ["a","b","c","t"]; var y = ["d","a","t","e","g"]; var z = []; $.each(y, function(idx, value){ if ($.inArray(value,x) == -1) { z.push(value); } }); ?alert(z); // should be ["d","e","g"] Here is the code in action. Any ideas?

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• PHP: simplify with algorithm?

  - by tshabala

  Hello. Here's a piece of PHP code I think is not very "pretty", I'm sure it's possible to simplify it with for or something. I'm trying to find and algorithm that would work for this, but I can't figure it out, please help me. Here's the code: if(isset($four)) { if(isset($navi[$one][$two][$three][$four])) echo "/content/" . $one . "/" . $two . "/" . $three . "/" .$four . ".php"; else echo "error"; } else if(isset($three)) { if(isset($navi[$one][$two][$three])) echo "/content/" . $one . "/" . $two . "/" . $three . ".php"; else echo "error"; } else if(isset($two)) { if(isset($navi[$one][$two])) echo "/content/" . $one . "/" . $two . ".php"; else echo "error"; } else if(isset($one)) { if(isset($navi[$one]))echo "/content/" . $one . ".php"; else echo "error"; } else { echo "error"; } Thanks!

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• Algorithm Question

  - by Ravi

  Hi, I am trying to find a O (n) algorithm for this problem but unable to do so even after spending 3 - 4 hours. The brute force method times out (O (n^2)). I am confused as to how to do it ? Does the solution requires dynamic programming solution ? http://acm.timus.ru/problem.aspx?space=1&num=1794 In short the problem is this: There are some students sitting in circle and each one of them has its own choice as to when he wants to be asked a question from a teacher. The teacher will ask the questions in clockwise order only. For example: 5 3 3 1 5 5 This means that there are 5 students and : 1st student wants to go third 2nd student wants to go third 3rd student wants to go first 4th student wants to go fifth 5th student wants to go fifth. The question is as to where should teacher start asking questions so that maximum number of students will get the turn as they want. For this particular example, the answer is 5 because 3 3 1 5 5 2 3 4 5 1 You can see that by starting at fifth student as 1st, 2 students (3 and 5) are getting the choices as they wanted. For this example the answer is 12th student : 12 5 1 2 3 6 3 8 4 10 3 12 7 because 5 1 2 3 6 3 8 4 10 3 12 7 2 3 4 5 6 7 8 9 10 11 12 1 four students get their choices fulfilled. Thanks Ravi

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• barebones sort algorithm

  - by user309322

  i have been asked to make a simple sort aglorithm to sort a random series of 6 numbers into numerical order. However i have been asked to do this using "Barebones" a theoretical language put forward in the Book Computer Science an overview. Some information on the language can be found here http://www.brouhaha.com/~eric/software/barebones/ Just to clarify i am a student teacher and have been doing anaysis on "mini-programing languages" and their uses in a teaching environment, i suggested to my tutor that i look at barebones and asked what sort of exmaple program i should write . He suggested a simple sort algorithm. Now since looking at the language i cant understand how i can do this without using arrays and if statements. The code to swap the value of variables would be while a not 0 do; incr Aux1; decr a; end; while b not 0 do; incr Aux2 decr b end; while Aux1 not 0 do; incr a; decr Aux1; end; while Aux2 not 0 do; incr b; decr Aux2; end; however the language does not provide < or operators

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• C# algorithm for figuring out different possible combinations...

  - by ttomsen

  I have 10 boxes, each box can hold one item from a group/type of items, each 'group' type only fits in one of the 10 box types. The pool can have n number of items. The groups have completely distinct items. Each item has a price, i want an algorithm that will generate all the different possibilities, so i can figure out different price points. so a smaller picture of the problem BOX A - can have item 1,2,3,4 in it BOX B - can have item 6,7,8,9,10,11,12 BOX C - can have item 13,15,16,20,21 The items are stored in a db, they have a column which denotes which box they can go in. All box types are stored in an array, and I can put the items in a generic list. Anyone see a straightforward way to do this. I have tried doing 10 nested foreach's to see if i could find a simpler way. The nested loops will take MANY hours to run. the nested for each's basically pull all combinations, then calculate a rank for each combination, and store the top 10 ranked combination of items for output

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• search algorithm using sentinel

  - by davit-datuashvili

  i am trying to do search algorithm using sentinel which reduce time to 3.87n nanoseconds for example compare to this code int search (int t ){ for (int i=0;i<n;i++) if (x[i]==t) return i; return -1; } it takes 4.06 nanoseconds so i am trying to optimize it here is code public class Search{ public static int search(int a[],int t){ int i; int p=0; int n=a.length; int hold; hold=a[n-1]; a[n-1]=t; for ( i=0;;i++) if (a[i]==t) break; a[n-1]=t; if (i==n){ p= -1; } else{ p= i; } return p; } public static void main(String[]args){ int t=-1; int a[]=new int[]{4,5,2,6,8,7,9}; System.out.println(search(a,t)); } } but is show me that 9 is at position 6 which is correct but if t =1 or something else which is not array it show me position 6 too please help

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• Questions about the Backpropogation Algorithm

  - by Colemangrill

  I have a few questions concerning backpropogation. I'm trying to learn the fundamentals behind neural network theory and wanted to start small, building a simple XOR classifier. I've read a lot of articles and skimmed multiple textbooks - but I can't seem to teach this thing the pattern for XOR. Firstly, I am unclear about the learning model for backpropogation. Here is some pseudo-code to represent how I am trying to train the network. [Lets assume my network is setup properly (ie: multiple inputs connect to a hidden layer connect to an output layer and all wired up properly)]. SET guess = getNetworkOutput() // Note this is using a sigmoid activation function. SET error = desiredOutput - guess SET delta = learningConstant * error * sigmoidDerivative(guess) For Each Node in inputNodes For Each Weight in inputNodes[n] inputNodes[n].weight[j] += delta; // At this point, I am assuming the first layer has been trained. // Then I recurse a similar function over the hidden layer and output layer. // The prime difference being that it further divi's up the adjustment delta. I realize this is probably not enough to go off of, and I will gladly expound on any part of my implementation. Using the above algorithm, my neural network does get trained, kind of. But not properly. The output is always XOR 1 1 [smallest number] XOR 0 0 [largest number] XOR 1 0 [medium number] XOR 0 1 [medium number] I can never train the [1,1] [0,0] to be the same value. If you have any suggestions, additional resources, articles, blogs, etc for me to look at I am very interested in learning more about this topic. Thank you for your assistance, I appreciate it greatly!

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• Search and Matching algorithm

  - by Tony

  Hello everyone. I am trying to come up with an algorithm to do the following: I have total 12 cells that I need to fill until program stops. I have 3 rows and each row has 4 columns. As an example, let me illustrate this as in airplane. So you have 3 rows and each row has 4 columns and you have window/aisle seats. Each row will have a window seat, aisle seat, aisle seat and window seat (|WA AW| Just like seat arrangement in airplane). At each iteration (different set of passengers), there would be some number of passengers (between 1 and 12) and I need to seat them closest together possible (Seat together). And I do this for next group (each iteration) until program stops (It will stop when I am done with every group). For example, I have 3 passengers (A,B,and C) and A wants to seat in Window, B wants to seat in Aisle and C wants to seat in Window. Assuming that all the seats (all 12) are available, I could place them like |A# BC| or |CB #A| and mark the seats dirty (so I don’t pick same seats again for next passengers). And I do this for next group (iteration). I am not sure if this right forum, but if somebody can advise me how I should accomplish, I would really appreciate it. Thanks.

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• Suggestions for opening the Rails toolbox to design a challenge game?

  - by keruilin

  How would you suggest designing a challenge system as part of a food-eating game so that it's automated as possible? All RoR tools, design patterns and logic are at your disposal (e.g., admin consoles, crontab, arch, etc.). Prize goes to whoever can suggest the simplest and most-automated design! Here are the requirements: User has many challenges. Badge has many challenges. (A unique badge is awarded for each challenge won.) Only one challenge can run at a time. Each challenge has a limited number of days that it runs. For example, one challenge can run 3 days, while another runs 7 days. Challenges can be seasonal. For example, "Eat 13 Pumpkins" only runs during the Fall. New challenges are added to the game on an ongoing basis. For example, a new challenge every week. Each challenge has a certain probability of being selected to run. For example, "Eat 10 Pies" challenge has 10% chance of being selected to run. As each new challenge is added to the database, I want the probabilities of running to change dynamically. I want to avoid the scenario where I'm manually updating a database field just to change the probability from 10% to 5%, for example. Challenges act like Easter eggs. Challenge icons pop-up at different places on the webpage. User is awarded a badge for successfully completing a challenge, but only when it's active. There is some wait time between each challenge. Between 1 and 7 days. Which wait time is random, but the probability of the wait time being short is high and the probability of it being a long wait time is low.

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• Algorithm: Find smallest subset containing K 0's

  - by Vishal

  I have array of 1's and 0's only. Now I want to find contiguous subset/subarray which contains at least K 0's. Example Array is 1 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 0 0 1 1 0 0 1 0 0 0 and K(6) should be 0 0 1 0 1 1 0 0 0 or 0 0 0 0 1 0 1 1 0.... My Solution Array: 1 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 0 0 1 1 0 0 Index: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Sum: 1 2 2 3 4 4 5 6 6 6 6 6 7 7 8 9 9 9 9 10 11 11 11 Diff(I-S): 0 0 1 1 1 2 2 2 3 4 5 6 6 7 7 7 8 9 10 10 10 11 12 For K(6) Start with 9-15 = Store difference in diff. Next increase difference 8-15(Difference in index) 8-14(Compare Difference in index) So on keep moving to find element with least elements... I am looking for better algorithm for this solution.

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• What makes my code DDD (domain-driven design) qualified?

  - by oykuo

  Hi All, I'm new to DDD and am thinking about using this design technique in my project. However, what strikes me about DDD is that how basic the idea is. Unlike other design techniques such as MVC and TDD, it doesn't seems to contain any ground breaking ideas. For example, I'm sure some of you will have the same feeling that the idea of root aggregates and repositories are nothing new because when you are was writing MVC web applications you have to have one single master object (i.e. the root aggregate) that contain other minor objects (i.e. value objects and entities) in the model layer in order to send data to a strongly typed view. To me, the only new idea in DDD is probably the "Smart" entities (i.e. you are supposed to have business rules on root aggregates) Separation between value object, root aggregate and entities. Can anyone tell me if I have missed out anything here? If that's all there is to DDD, if I update one of my existing MVC application with the above 2 new ideas, can I claim it's an TDD, MVC and DDD applcation?

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• Elegant Algorithm for Parsing Data Stream Into Record

  - by Matt Long

  I am interfacing with a hardware device that streams data to my app over Wifi. The data is streaming in just fine. The data contains a character header (DATA:) that indicates a new record has begun. The issues is that the data I receive doesn't necessarily fall on the header boundary, so I have to capture the data until what I've captured contains the header. Then, everything that precedes the header goes into the previous record and everything that comes after it goes into a new record. I have this working, but wondered if anyone has done this before and has a good computer-sciencey way to solve the problem. Here's what I do: Convert the NSData of the current read to an NSString Append the NSString to a placeholder string Check placeholder string for the header (DATA:). If the header is not there, just wait for the next read. If the header exists, append whatever precedes it to a previous record placeholder and hand that placeholder off to an array as a complete record that I can further parse into fields. Take whatever shows up after the header and place it in the record placeholder so that it can be appended to in the next read. Repeat steps 3 - 5. Let me know if you see any flaws with this or have a suggestion for a better way. Seems there should be some design pattern for this, but I can't think of one. Thanks.

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• Software or Photoshop plugins for professional photo album design

  - by Iain Fraser

  I am a graphic designer (among other things) and I'm used to doing magazine advertisements, brochures, posters and that sort of thing. Recently I was approached by a photographer who wants a graphic designer to produce wedding albums for him. I have already done a couple for him but I'm finding it hard to work by just arranging my layouts in Photoshop alone. It's very time consuming, but quite repetitive - especially when you're dealing with common page layouts. I know a lot of photographers use album design software to speed up the process a bit. What's the industry standard in terms of album design software?

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• Design Pattern Books, Papers or Resources for Non-Object Orientated Paradigms?

  - by FinnNk

  After viewing this video on InfoQ about functional design patterns I was wondering what resources are out there on design patterns for non-object orientated paradigms. There are plenty out there for the OO world (GOF, etc, etc) and for architecture (EoEAA, etc, etc) but I'm not aware of what's out there for functional, logic, or other programming paradigms. Is there anything? A comment during the video suggests possibly not - does anyone know better? (By the way, by design patterns I don't mean language features or data structures but higher level approaches to designing an application - as discussed in the linked video)

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• Should I use the factory design pattern for every class?

  - by Frog

  I've been writing a website in PHP. As the code becomes more complex, I keep finding problems that can be solved using the factory design pattern. For example: I've a got a class Page which has subclasses HTMLPage, XMLPage, etc. Depending on some input I need to return an object of either one of these classes. I use the factory design pattern to do this. But as I encounter this problem in more classes, I keep having to change code which still initiates an object using its constructor. So now I'm wondering: is it a good idea to change all code so that it uses the factory design pattern? Or are there big drawbacks? I'm currently in a position to change this, so your answers would be really helpful.

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• Is the structure used for these web pages a design pattern?

  - by aspdotnetuser

  I want to know if the structure for an ASP.NET website I'm working on uses a design pattern for it's web pages. If it is a design pattern, what is it called? The web pages have the following structure: UserDetails page (UserDetails.aspx) - includes UserDetailsController.ascx user control. UserDetailsController.ascx includes sub user controls like UserAccountDetails.ascx and UserLoginDetails.ascx etc Each sub user control contains a small amount of code/logic, the 'controller' user controls that host these sub user controls (i.e UserDetailsController.ascx) appear to call the business rules code and pass the data to the sub user controls. Is this a design pattern? What is it called?

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• How do you enhance your websites speed without compromising the design and access?

  - by Thorn007

  How do you enhance your websites load speed without killing the design and accessibility? File compression, CDN, Gzip? What are the best tools for doing so? For example, Google has optimized their site without compromising the design. Also, many website can kill the purity of their images with compression. Is there a way, more or lest best practice, to increase speed without compromising the design and accessibility? Note: sorry for being so vague but I don't know how else to phrase this question.

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• Where should I ask for feedbacks about web design? [closed]

  - by mariosangiorgio

  Possible Duplicate: Where can I get my website critiqued I am developing my personal website and I'd like to have feedbacks about its design. Is there any site/forum you would recommend me? I know that the best solution would be to hire a professional web designer and have him design my website, but I am also interested in understanding how to improve my design skills. Of course any recommended book, website, resource is more than welcome. I am not posting here the link to my home page because I think this Q/A site is more about web-development in general, but if you'd like to see my personal page and give some feedback I'll link it.

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• Issue with angular gradient algorithm

  - by user146780

  I have an angular gradient algorithm: GLuint OGLENGINEFUNCTIONS::CreateAngularGradient( std::vector<ARGBCOLORF> &input,POINTFLOAT start, POINTFLOAT end, int width, int height ) { std::vector<GLubyte> pdata(width * height * 4); float pi = 3.1415; float cx; float cy; float r1; float r2; float ang; float px; float py; float t; cx = start.x; cy = start.y; r1 = 0; r2 = 500; ang = end.x / 100; ARGBCOLORF color; for (unsigned int i = 0; i < height; i++) { for (unsigned int j = 0; j < width; j++) { px = j; py = i; if( px * px + py * py <= r2 * r2 && px * px + py * py >= r1 * r1 ) { t= atan2(py-cy,px-cx) + ang; t= t+ pi; if (t > 2* pi) { t=t-2*pi; t=t/(2*pi); } } //end + start color.r = (0 * t) + (120 * (1 - t)); color.g = (50 * t) + (255 * (1 - t)); color.b = (0 * t) + (50 * (1 - t)); color.a = (255 * t) + (200 * (1 - t)); pdata[i * 4 * width + j * 4 + 0] = (GLubyte) color.r; pdata[i * 4 * width + j * 4 + 1] = (GLubyte) color.g; pdata[i * 4 * width + j * 4 + 2] = (GLubyte) 12; pdata[i * 4 * width + j * 4 + 3] = (GLubyte) 255; } } It works fine except the ang variable only controls the end sweep, not the start sweep. The start sweep is always facing the middle left as seen here: http://img810.imageshack.us/img810/9623/uhoh.png Basically I have no control over the end one going this <- way. How could I control this one? Thanks

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• Algorithm to Render a Horizontal Binary-ish Tree in Text/ASCII form

  - by Justin L.

  It's a pretty normal binary tree, except for the fact that one of the nodes may be empty. I'd like to find a way to output it in a horizontal way (that is, the root node is on the left and expands to the right). I've had some experience expanding trees vertically (root node at the top, expanding downwards), but I'm not sure where to start, in this case. Preferably, it would follow these couple of rules: If a node has only one child, it can be skipped as redundant (an "end node", with no children, is always displayed) All nodes of the same depth must be aligned vertically; all nodes must be to the right of all less-deep nodes and to the left of all deeper nodes. Nodes have a string representation which includes their depth. Each "end node" has its own unique line; that is, the number of lines is the number of end nodes in the tree, and when an end node is on a line, there may be nothing else on that line after that end node. As a consequence of the last rule, the root node should be in either the top left or the bottom left corner; top left is preferred. For example, this is a valid tree, with six end nodes (node is represented by a name, and its depth): [a0]------------[b3]------[c5]------[d8] \ \ \----------[e9] \ \----[f5] \--[g1]--------[h4]------[i6] \ \--------------------[j10] \-[k3] Which represents the horizontal, explicit binary tree: 0 a / \ 1 g * / \ \ 2 * * * / \ \ 3 k * b / / \ 4 h * * / \ \ \ 5 * * f c / \ / \ 6 * i * * / / \ 7 * * * / / \ 8 * * d / / 9 * e / 10 j (branches folded for compactness; * representing redundant, one-child nodes; note that *'s are actual nodes, storing one child each, just with names omitted here for presentation sake) (also, to clarify, I'd like to generate the first, horizontal tree; not this vertical tree) I say language-agnostic because I'm just looking for an algorithm; I say ruby because I'm eventually going to have to implement it in ruby anyway. Assume that each Node data structure stores only its id, a left node, and a right node. A master Tree class keeps tracks of all nodes and has adequate algorithms to find: A node's nth ancestor A node's nth descendant The generation of a node The lowest common ancestor of two given nodes Anyone have any ideas of where I could start? Should I go for the recursive approach? Iterative?

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• Algorithm to retrieve every possible combination of sublists of a two lists

  - by sgmoore

  Suppose I have two lists, how do I iterate through every possible combination of every sublist, such that each item appears once and only once. I guess an example could be if you have employees and jobs and you want split them into teams, where each employee can only be in one team and each job can only be in one team. Eg List<string> employees = new List<string>() { "Adam", "Bob"} ; List<string> jobs = new List<string>() { "1", "2", "3"}; I want Adam : 1 Bob : 2 , 3 Adam : 1 , 2 Bob : 3 Adam : 1 , 3 Bob : 2 Adam : 2 Bob : 1 , 3 Adam : 2 , 3 Bob : 1 Adam : 3 Bob : 1 , 2 Adam, Bob : 1, 2, 3 I tried using the answer to this stackoverflow question to generate a list of every possible combination of employees and every possible combination of jobs and then select one item from each from each list, but that's about as far as I got. I don't know the maximum size of the lists, but it would be certainly be less than 100 and there may be other limiting factors (such as each team can have no more than 5 employees) Update Not sure whether this can be tidied up more and/or simplified, but this is what I have ended up with so far. It uses the Group algorithm supplied by Yorye (see his answer below), but I removed the orderby which I don't need and caused problems if the keys are not comparable. var employees = new List<string>() { "Adam", "Bob" } ; var jobs = new List<string>() { "1", "2", "3" }; int c= 0; foreach (int noOfTeams in Enumerable.Range(1, employees.Count)) { var hs = new HashSet<string>(); foreach( var grouping in Group(Enumerable.Range(1, noOfTeams).ToList(), employees)) { // Generate a unique key for each group to detect duplicates. var key = string.Join(":" , grouping.Select(sub => string.Join(",", sub))); if (!hs.Add(key)) continue; List<List<string>> teams = (from r in grouping select r.ToList()).ToList(); foreach (var group in Group(teams, jobs)) { foreach (var sub in group) { Console.WriteLine(String.Join(", " , sub.Key ) + " : " + string.Join(", ", sub)); } Console.WriteLine(); c++; } } } Console.WriteLine(String.Format("{0:n0} combinations for {1} employees and {2} jobs" , c , employees.Count, jobs.Count)); Since I'm not worried about the order of the results, this seems to give me what I need.

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• Algorithm for finding symmetries of a tree

  - by Paxinum

  I have n sectors, enumerated 0 to n-1 counterclockwise. The boundaries between these sectors are infinite branches (n of them). The sectors live in the complex plane, and for n even, sector 0 and n/2 are bisected by the real axis, and the sectors are evenly spaced. These branches meet at certain points, called junctions. Each junction is adjacent to a subset of the sectors (at least 3 of them). Specifying the junctions, (in pre-fix order, lets say, starting from junction adjacent to sector 0 and 1), and the distance between the junctions, uniquely describes the tree. Now, given such a representation, how can I see if it is symmetric wrt the real axis? For example, n=6, the tree (0,1,5)(1,2,4,5)(2,3,4) have three junctions on the real line, so it is symmetric wrt the real axis. If the distances between (015) and (1245) is equal to distance from (1245) to (234), this is also symmetric wrt the imaginary axis. The tree (0,1,5)(1,2,5)(2,4,5)(2,3,4) have 4 junctions, and this is never symmetric wrt either imaginary or real axis, but it has 180 degrees rotation symmetry if the distance between the first two and the last two junctions in the representation are equal. Edit: This is actually for my research. I have posted the question at mathoverflow as well, but my days in competition programming tells me that this is more like an IOI task. Code in mathematica would be excellent, but java, python, or any other language readable by a human suffices. Here are some examples (pretend the double edges are single and we have a tree) http://www2.math.su.se/~per/files.php?file=contr_ex_1.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_2.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_5.pdf Example 1 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,3). Example 2 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,1). Example 5 is described as (0,1,4,5)(1,2,3,4) with distances (2). So, given the description/representation, I want to find some algorithm to decide if it is symmetric wrt real, imaginary, and rotation 180 degrees. The last example have 180 degree symmetry. (These symmetries corresponds to special kinds of potential in the Schroedinger equation, which has nice properties in quantum mechanics.)

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• Php algorithm - How to achieve that without eval

  - by Marcelo

  I have a class that keeps data stores/access data by using words.separated.by.dots keys and it behaves like the following: $object = new MyArray() $object->setParam('user.name','marcelo'); $object->setParam('user.email','[email protected]'); $object->getParams(); /* array( 'user' => array( 'name' => 'marcelo', 'email' => '[email protected]' ) ); */ It is working, but the method unsetParam() was horribly implemented. That happened because i didn't know how to achieve that without eval() function. Although it is working, I found that it was a really challenging algorithm and that you might find fun trying to achieve that without eval(). class MyArray { /** * @param string $key * @return Mura_Session_Abstract */ public function unsetParam($key) { $params = $this->getParams(); $tmp = $params; $keys = explode('.', $key); foreach ($keys as $key) { if (!isset($tmp[$key])) { return $this; } $tmp = $tmp[$key]; } // bad code! $eval = "unset(\$params['" . implode("']['", $keys) . "']);"; eval($eval); $this->setParams($params); return $this; } } The test method: public function testCanUnsetNestedParam() { $params = array( '1' => array( '1' => array( '1' => array( '1' => 'one', '2' => 'two', '3' => 'three', ), '2' => array( '1' => 'one', '2' => 'two', '3' => 'three', ), ) ), '2' => 'something' ); $session = $this->newSession(); $session->setParams($params); unset($params['1']['1']['1']); $session->unsetParam('1.1.1'); $this->assertEquals($params, $session->getParams()); $this->assertEquals($params['1']['1']['2'], $session->getParam('1.1.2')); }

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