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  • Fair 2-combinations

    - by Tometzky
    I need to fairly assign 2 experts from x experts (x is rather small - less than 50) for every n applications, so that: each expert has the same number of applications (+-1); each pair of experts (2-combination of x) has the same number of applications (+-1); It is simple to generate all 2-combinations: for (i=0; i<n; i++) { for (j=i+1; j<n; j++) { combinations.append(tuple(i,j)); } } But to assign experts fairly I need to assign a combination to an application i correct order, for example: experts: 0 1 2 3 4 fair combinations: counts 01234 01 11000 23 11110 04 21111 12 22211 34 22222 02 32322 13 33332 14 34333 03 44343 24 44444 I'm unable to come up with a good algorithm for this (the best I came up with is rather complicated and with O(x4) complexity). Could you help me?

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  • How can I approach creating an efficient algorithm for maximizing value with these specific constraints?

    - by sway
    I'm having trouble coming up with an approach that isn't n^2 for this problem. Here's a contrived, simplified version I've come up with: Let's say you're a company that needs 4 employees to launch in a new city, a manager, two salespeople, and a customer support rep, and you magically know how much impact every candidate will have and how much salary they require to take the job. Your table of potential employees looks something like this: Name Position Salary Impact Adam Smith Manager 60,000 11 Allison Brown Salesperson 40,000 9 Brad Stewart Manager 55,000 9 ...etc (thousands of records) What algorithmic approach can be taken to find the maximum "impact" while still filling all the positions and remaining under, say, a 200,000 budget? Thanks!

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  • Building general programming skills?

    - by toleero
    Hello :) I currently am quite new to programming, I've had exposure to a few languages (C#, PHP, JavaScript, VB, and some others) and I'm quite new to OOP. I was just wondering what is the best way to build up general programming/problem solving skills without being language specific? I was thinking maybe of something like Project Euler but more geared towards newbies? Thanks! Edit: I am looking at getting into Game Scripting/Programming, I'm already in Games but in a different discipline :)

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  • Can anyone help solve this complex algorithmic problem?

    - by Locaaaaa
    I got this question in an interview and I was not able to solve it. You have a circular road, with N number of gas stations. You know the ammount of gas that each station has. You know the ammount of gas you need to GO from one station to the next one. Your car starts with 0. The question is: Create an algorithm, to know from which gas station you must start driving. As an exercise to me, I would translate the algorithm to C#.

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  • How to get better at solving Dynamic programming problems

    - by newbie
    I recently came across this question: "You are given a boolean expression consisting of a string of the symbols 'true', 'false', 'and', 'or', and 'xor'. Count the number of ways to parenthesize the expression such that it will evaluate to true. For example, there is only 1 way to parenthesize 'true and false xor true' such that it evaluates to true." I knew it is a dynamic programming problem so i tried to come up with a solution on my own which is as follows. Suppose we have a expression as A.B.C.....D where '.' represents any of the operations and, or, xor and the capital letters represent true or false. Lets say the number of ways for this expression of size K to produce a true is N. when a new boolean value E is added to this expression there are 2 ways to parenthesize this new expression 1. ((A.B.C.....D).E) ie. with all possible parenthesizations of A.B.C.....D we add E at the end. 2. (A.B.C.(D.E)) ie. evaluate D.E first and then find the number of ways this expression of size K can produce true. suppose T[K] is the number of ways the expression with size K produces true then T[k]=val1+val2+val3 where val1,val2,val3 are calculated as follows. 1)when E is grouped with D. i)It does not change the value of D ii)it inverses the value of D in the first case val1=T[K]=N.( As this reduces to the initial A.B.C....D expression ). In the second case re-evaluate dp[K] with value of D reversed and that is val1. 2)when E is grouped with the whole expression. //val2 contains the number of 'true' E will produce with expressions which gave 'true' among all parenthesized instances of A.B.C.......D i) if true.E = true then val2 = N ii) if true.E = false then val2 = 0 //val3 contains the number of 'true' E will produce with expressions which gave 'false' among all parenthesized instances of A.B.C.......D iii) if false.E=true then val3=( 2^(K-2) - N ) = M ie. number of ways the expression with size K produces a false [ 2^(K-2) is the number of ways to parenthesize an expression of size K ]. iv) if false.E=false then val3 = 0 This is the basic idea i had in mind but when i checked for its solution http://people.csail.mit.edu/bdean/6.046/dp/dp_9.swf the approach there was completely different. Can someone tell me what am I doing wrong and how can i get better at solving DP so that I can come up with solutions like the one given above myself. Thanks in advance.

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  • Nearest color algorithm using Hex Triplet

    - by Lijo
    Following page list colors with names http://en.wikipedia.org/wiki/List_of_colors. For example #5D8AA8 Hex Triplet is "Air Force Blue". This information will be stored in a databse table (tbl_Color (HexTriplet,ColorName)) in my system Suppose I created a color with #5D8AA7 Hex Triplet. I need to get the nearest color available in the tbl_Color table. The expected anaser is "#5D8AA8 - Air Force Blue". This is because #5D8AA8 is the nearest color for #5D8AA7. Do we have any algorithm for finding the nearest color? How to write it using C# / Java? REFERENCE http://stackoverflow.com/questions/5440051/algorithm-for-parsing-hex-into-color-family http://stackoverflow.com/questions/6130621/algorithm-for-finding-the-color-between-two-others-in-the-colorspace-of-painte Suggested Formula: Suggested by @user281377. Choose the color where the sum of those squared differences is minimal (Square(Red(source)-Red(target))) + (Square(Green(source)-Green(target))) +(Square(Blue(source)-Blue(target)))

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  • Ways to dynamically render a real world 3d environment in Unity3D

    - by Jake M
    Using Unity3D and C# I am attempting to display a 3d version of a real world location. Inside my Unity3D app, the user will specify the GPS coordinates of a location, then my app will have to generate a 3d plane(anything doesn't have to be a plane) of that location. The plane will show a 500 metre by 500 metre 3d snapshot of that location. How would you suggest I achieve this in Unity3D? What methodology would you use to achieve this? NOTE: I understand that this is a very difficult endevour(to render real world locations dynamically in Unity3d) so I expect to perform many actions to achieve this. I just don't know of all the technologies out there and which would be best for my needs For example: Suggested methodology 1: Prompt user to specify GPS coords Use Google earth API and HTTP to programmatically obtain a .khm file describing that location(Not sure if google earth provides that capability does it?) Unzip the .khm so I have the .dae file Convert that file to a .3ds file using ??? third party converter(is there a converter that exists?) Import .3ds into Unity3D at runtime as a plane(is this possible)? Suggested methodology 2: Prompt user to specify GPS coords Use Google earth API and HTTP to programmatically obtain a .khm file describing that location(Not sure if google earth provides that capability does it?) Unzip the .khm so I have the .dae file Parse .dae file using my own C# parser I will write(do you think its possible to write a .dae parser that can parse the .dae into an array of Vector3 that describe the height map of that location?) Dynamically create a plane in Unity3D and populate it with my array/list of Vector3 points(is it possible to create a plane this way?) Maybe I am meant to create a mesh instead of a plane? Can you think of any other ways I could render a real world 3d environment in Unity3D?

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  • Checking whether php script was resolved by optimal way

    - by user2135931
    Can anybody give some advise how to check the arbitrary php code on optimal solution. For example I create a simple algorithm and sent it on the special resource. After proccessing my algorithm this resource give me result whether my code is nice. If no it give me some advice and tell what is wrong (maybe I forgot check devision by zero etc). I looked for php code analyzer but could't find any variants. Maybe someone give me a resource where I can research this problem. Thanks in advance!

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  • How many copies are needed to enlarge an array?

    - by user10326
    I am reading an analysis on dynamic arrays (from the Skiena's algorithm manual). I.e. when we have an array structure and each time we are out of space we allocate a new array of double the size of the original. It describes the waste that occurs when the array has to be resized. It says that (n/2)+1 through n will be moved at most once or not at all. This is clear. Then by describing that half the elements move once, a quarter of the elements twice, and so on, the total number of movements M is given by: This seems to me that it adds more copies than actually happen. E.g. if we have the following: array of 1 element +--+ |a | +--+ double the array (2 elements) +--++--+ |a ||b | +--++--+ double the array (4 elements) +--++--++--++--+ |a ||b ||c ||c | +--++--++--++--+ double the array (8 elements) +--++--++--++--++--++--++--++--+ |a ||b ||c ||c ||x ||x ||x ||x | +--++--++--++--++--++--++--++--+ double the array (16 elements) +--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--+ |a ||b ||c ||c ||x ||x ||x ||x || || || || || || || || | +--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--+ We have the x element copied 4 times, c element copied 4 times, b element copied 4 times and a element copied 5 times so total is 4+4+4+5 = 17 copies/movements. But according to formula we should have 1*(16/2)+2*(16/4)+3*(16/8)+4*(16/16)= 8+8+6+4=26 copies of elements for the enlargement of the array to 16 elements. Is this some mistake or the aim of the formula is to provide a rough upper limit approximation? Or am I missunderstanding something here?

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  • Monkey Hunter algorithm - Interview question [closed]

    - by Estefany Velez
    Question asked in an Interview: You are a hunter in the forest. A monkey is in the trees, but you don't know where and you can't see it. You can shoot at the trees, you have unlimited ammunition. Immediately after you shoot at a tree, if the monkey was in the tree, he falls and you win. If the monkey was not in the tree, he jumps (randomly) to an adjacent tree (he has to). Find an algorithm to get the monkey in the fewest shots possible. SOLUTION: The correct answer according to me was in the comments, credit to @rtperson: You could eliminate this possibility by shooting each tree twice as you sweep left, giving you a worst case of O(2n). EDIT: ...that is, a worst case of O(2n-1). You don't need to shoot the last tree twice.

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  • algorithm for project euler problem no 18

    - by Valentino Ru
    Problem number 18 from Project Euler's site is as follows: By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23. 3 7 4 2 4 6 8 5 9 3 That is, 3 + 7 + 4 + 9 = 23. Find the maximum total from top to bottom of the triangle below: 75 95 64 17 47 82 18 35 87 10 20 04 82 47 65 19 01 23 75 03 34 88 02 77 73 07 63 67 99 65 04 28 06 16 70 92 41 41 26 56 83 40 80 70 33 41 48 72 33 47 32 37 16 94 29 53 71 44 65 25 43 91 52 97 51 14 70 11 33 28 77 73 17 78 39 68 17 57 91 71 52 38 17 14 91 43 58 50 27 29 48 63 66 04 68 89 53 67 30 73 16 69 87 40 31 04 62 98 27 23 09 70 98 73 93 38 53 60 04 23 NOTE: As there are only 16384 routes, it is possible to solve this problem by trying every route. However, Problem 67, is the same challenge with a triangle containing one-hundred rows; it cannot be solved by brute force, and requires a clever method! ;o) The formulation of this problems does not make clear if the "Traversor" is greedy, meaning that he always choosed the child with be higher value the maximum of every single walkthrough is asked The NOTE says, that it is possible to solve this problem by trying every route. This means to me, that is is also possible without! This leads to my actual question: Assumed that not the greedy one is the max, is there any algorithm that finds the max walkthrough value without trying every route and that doesn't act like the greedy algorithm? I implemented an algorithm in Java, putting the values first in a node structure, then applying the greedy algorithm. The result, however, is cosidered as wrong by Project Euler. sum = 0; void findWay(Node node){ sum += node.value; if(node.nodeLeft != null && node.nodeRight != null){ if(node.nodeLeft.value > node.nodeRight.value){ findWay(node.nodeLeft); }else{ findWay(node.nodeRight); } } }

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  • Algorithm to Solve Most of a Problem

    - by Mike G
    I need an Algorithm/Design Pattern that allows me to try to get the maximum number of rules followed. So I have a couple teams and I need to pair them with a referee and against each other into a round robin. There a rules on who can compete with who and who can judge who so I need to find the configuration that satisfies the most of these. Some rules are more important than others and are "worth more" when evaluating "what satisfies the most of them" There probably isn't a algorithm for this, but is there a design pattern that could help me maximize my chances of finding this configuration?

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  • Quickly compute added and removed lines

    - by Philippe Marschall
    I'm trying to compare two text files. I want to compute how many lines were added and removed. Basically what git diff --stat is doing. Bonus points for not having to store the entire file contents in memory. The approach I'm currently having in mind is: read each line of the old file compute a hash (probably MD5 or SHA-1) for each line store the hashes in a set do the same for each line in the new file every hash from the old file set that's missing in the new file set was removed every hash from the new file set that's missing in the old file set was added I'll probably want to exclude empty and all white space lines. There is a small issue with duplicated lines. This can either be solved by additionally storing how often a hash appears or comparing the number of lines in the old and new file and adjust either the added or removed lines so that the numbers add up. Do you see room for improvements or a better approach?

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  • I have a stacktrace and limit of 250 characters for a bug report

    - by George Duckett
    I'm developing an xbox indie game and as a last-resort I have a try...catch encompassing everything. At this point if an exception is raised I can get the user to send me a message through the xbox however the limit is 250 characters. How can I get the most value out of my 250 characters? I don't want to do any encoding / compressing at least initially. Any solution to this problem could be compressed if needed as a second step anyway. I'm thinking of doing things like turning this: at EasyStorage.SaveDevice.VerifyIsReady() at EasyStorage.SaveDevice.Save(String containerName, String fileName) into this (drop the repeated namespace/class and method parameter names): at EasyStorage.SaveDevice.VerifyIsReady() at ..Save(String, String) Or maybe even just including the inner-most method, then only line numbers up the stack etc. TL;DR: Given an exception with a stacktrace how would you get the most useful debugging infromation out of 250 characters? (It will be a .net exception/stacktrace)

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  • Detect duplicate in a subset from a set of elements

    - by Abhinav Shrivastava
    I have a set of numbers say : 1 1 2 8 5 6 6 7 8 8 4 2... I want to detect the duplicate element in subsets(of given size say k) of the above numbers... For example : Consider the increasing subsets(for example consider k=3) Subset 1 :{1,1,2} Subset 2 :{1,2,8} Subset 3 :{2,8,5} Subset 4 :{8,5,6} Subset 5 :{5,6,6} Subset 6 :{6,6,7} .... .... So my algorithm should detect that subset 1,5,6 contains duplicates.. My approach : 1)Copy the 1st k elements to a temporary array(vector) 2) using #include file in C++ STL...using unique() I would determine if there's any change in size of vector.. Any other clue how to approach this problem..

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  • Need suggestion for Mutiple Windows application design

    - by King Chan
    This was previously posted in StackOverflow, I just moved to here... I am using VS2008, MVVM, WPF, Prism to make a mutiple window CRM Application. I am using MidWinow in my MainWindow, I want Any ViewModel would able to make request to MainWindow to create/add/close MidChildWindow, ChildWindow(from WPF Toolkit), Window (the Window type). ViewModel can get the DialogResult from the ChildWindow its excutes. MainWindow have control on all opened window types. Here is my current approach: I made Dictionary of each of the windows type and stores them into MainWindow class. For 1, i.e in a CustomerInformationView, its CustomerInformationViewModel can execute EditCommand and use EventAggregator to tell MainWindow to open a new ChildWindow. CustomerInformationViewModel: CustomerEditView ceView = new CustomerEditView (); CustomerEditViewModel ceViewModel = CustomerEditViewModel (); ceView.DataContext = ceViewModel; ChildWindow cWindow = new ChildWindow(); cWindow.Content = ceView; MainWindow.EvntAggregator.GetEvent<NewWindowEvent>().Publish(new WindowEventArgs(ceViewModel.ViewModeGUID, cWindow )); cWindow.Show(); Notice that all my ViewModel will generates a Guid for help identifies the ChildWindow from MainWindow's dictionary. Since I will only be using 1 View 1 ViewModel for every Window. For 2. In CustomerInformationViewModel I can get DialogResult by OnClosing event from ChildWindow, in CustomerEditViewModel can use Guid to tell MainWindow to close the ChildWindow. Here is little question and problems: Is it good idea to use Guid here? Or should I use HashKey from ChildWindow? My MainWindows contains windows reference collections. So whenever window close, it will get notifies to remove from the collection by OnClosing event. But all the Windows itself doesn't know about its associated Guid, so when I remove it, I have to search for every KeyValuePair to compares... I still kind of feel wrong associate ViewModel's Guid for ChildWindow, it would make more sense if ChildWindow has it own ID then ViewModel associate with it... But most important, is there any better approach on this design? How can I improve this better?

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  • Algorithm to measure how "diffused" 5,000 pennies are in an economy?

    - by makerofthings7
    Please allow me to use this example/metaphor to describe an algorithm I need. Objects There are 5 thousand pennies. There are 50 cups. There is a tracking history (Passport "stamp" etc) that is associated with each penny as it moves between cups. Definition I'll define a "highly diffused" penny as one that passes through many cups. A "poorly diffused" penny is one that either passes back and forth between 2 cups Question How can I objectively measure the diffusion of a penny as: The number of moves the penny has gone through The number of cups the penny has been in A unit of time (day, week, month) Why am I doing this? I want to detect if a cup is hoarding pennies. Resistance from bad actors Since hoarding is bad, the "bad cup" may simply solicit a partner and simply move pennies between each other. This will reduce the amount of time a coin isn't in transit, and would skew hoarding detection. A solution might be to detect if a cup (or set of cups) are common "partners" with each other, though I'm not sure how to think though this problem. Broad applicability Any assistance would be helpful, since I would think that this algorithm is common to Economics The study of migration patterns of animals, citizens of a country Other natural occurring phenomena ... and probably exists as a term or concept I'm unfamiliar with.

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  • Microsoft Interview Preparation

    - by Manish
    I have 8 years of java background. Need help in identifying topics I need to prepare for Microsoft interview. I need to know how many rounds Microsoft will have and what all things these rounds consist of. I have identified the following topics. Please let me know if I need to prepare anything else as well. Arrays Linked Lists Recursion Stacks Queue Trees Graph -- What all I should prepare here Dynamic Programming -- again what all I need to prepare Sorting, Searching String Algos

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  • How does one unit test an algorithm

    - by Asa Baylus
    I was recently working on a JS slideshow which rotates images using a weighted average algorithm. Thankfully, timgilbert has written a weighted list script which implements the exact algorithm I needed. However in his documentation he's noted under todos: "unit tests!". I'd like to know is how one goes about unit testing an algorithm. In the case of a weighted average how would you create a proof that the averages are accurate when there is the element of randomness? Code samples of similar would be very helpful to my understanding.

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  • How can I keep directories in sync

    - by Guillaume Boudreau
    I have a directory, dirA, that users can work in: they can create, modify, rename and delete files & sub-directores in dirA. I want to keep another directory, dirB, in sync with dirA. What I'd like, is a discussion on finding a working algorithm that would achieve the above, with the limitations listed below. Requirements: 1. Something asynchronous - I don't want to stop file operations in dirA while I work in dirB. 2. I can't assume that I can just blindly rsync dirA to dirB on regular interval - dirA could contain millions of files & directories, and terrabytes of data. Completely walking the dirA tree could take hours. Those two requirements makes this really difficult. Having it asynchronous means that when I start working on a specific file from dirA, it might have moved a lot since it appeared. And the second limitation means that I really need to watch dirA, and work on atomic file operations that I notice. Current (broken) implementation: 1. Log all file & directory operations in dirA. 2. Using a separate process, read that log, and 'repeat' all the logged operations in dirB. Why is it broken: echo 1 > dirA/file1 # Allow the 'log reader' process to create dirB/file1: log = "write dirA/file1"; action = cp dirA/file1 dirB/file1; result = OK echo 1 > dirA/file2 mv dirA/file1 dirA/file3 mv dirA/file2 dirA/file1 rm dirA/file3 # End result: file1 contains '1' # 'log reader' process starts working on the 4 above file operations: log = "write file2"; action = cp dirA/file2 dirB/file2; result = failed: there is no dirA/file2 log = "rename file1 file3"; action = mv dirB/file1 dirB/file3; result = OK log = "rename file2 file1"; action = mv dirB/file2 dirB/file1; result = failed: there is no dirB/file2 log = "delete file3"; action = rm dirB/file3; result = OK # End result in dirB: no more files! Another broken example: echo 1 > dirA/dir1/file1 mv dirA/dir1 dirA/dir2 # 'log reader' process starts working on the 2 above file operations: log = "write file1"; action = cp dirA/dir1/file1 dirB/dir1/file1; result = failed: there is no dirA/dir1/file1 log = "rename dir1 dir2"; action = mv dirB/dir1 dirB/dir2; result = failed: there is no dirA/dir1 # End result if dirB: nothing!

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  • Application qos involving priority and bandwidth

    - by Steve Peng
    Our manager wants us to do applicaiton qos which is quite different from the well-known system qos. We have many services of three types, they have priorites, the manager wants to suspend low priority services requests when there are not enough bandwidth for high priority services. But if the high priority services requests decrease, the bandwidth for low priority services should increase and low priority service requests are allowed again. There should be an algorithm involving priority and bandwidth. I don't know how to design the algorithm, is there any example on the internet? Somebody can give suggestion? Thanks. UPDATE All these services are within a same process. We are setting the maximum bandwidth for the three types of services via ports of services via TC (TC is the linux qos tool whose name means traffic control).

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  • Finding links among many written and spoken thoughts

    - by Peter Fren
    So... I am using a digital voice recorder to record anything I see important, ranging from business to private, from rants to new business ideas. Every finalized idea is one wma-file. I wrote a program to sort the wma-files into folders. From time to time I listen to the wma-files, convert them to text(manually) and insert them into a mindmap with mindmanager, which I sort hierarchically by area and type in turn. This works very well, no idea is being lost, when I am out of ideas for a special topic, I listen to what I said and can get started again. What could a search system look like that finds links between thoughts(written in the mindmap and in the wma files) or in general gives me good search results even when the keyword I searched for is not present but a synonym of it or related topic(for instance flower should output entries containing orchid aswell, even if they contain orchid but not the very keyword flower). I prefer something ready-made but small adjustments to a given system are fine aswell. How would you approach this task?

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  • What is this algorithm for converting strings into numbers called?

    - by CodexArcanum
    I've been doing some work in Parsec recently, and for my toy language I wanted multi-based fractional numbers to be expressible. After digging around in Parsec's source a bit, I found their implementation of a floating-point number parser, and copied it to make the needed modifications. So I understand what this code does, and vaguely why (I haven't worked out the math fully yet, but I think I get the gist). But where did it come from? This seems like a pretty clever way to turn strings into floats and ints, is there a name for this algorithm? Or is it just something basic that's a hole in my knowledge? Did the folks behind Parsec devise it? Here's the code, first for integers: number' :: Integer -> Parser Integer number' base = do { digits <- many1 ( oneOf ( sigilRange base )) ; let n = foldl (\x d -> base * x + toInteger (convertDigit base d)) 0 digits ; seq n (return n) } So the basic idea here is that digits contains the string representing the whole number part, ie "192". The foldl converts each digit individually into a number, then adds that to the running total multiplied by the base, which means that by the end each digit has been multiplied by the correct factor (in aggregate) to position it. The fractional part is even more interesting: fraction' :: Integer -> Parser Double fraction' base = do { digits <- many1 ( oneOf ( sigilRange base )) ; let base' = fromIntegral base ; let f = foldr (\d x -> (x + fromIntegral (convertDigit base d))/base') 0.0 digits ; seq f (return f) Same general idea, but now a foldr and using repeated division. I don't quite understand why you add first and then divide for the fraction, but multiply first then add for the whole. I know it works, just haven't sorted out why. Anyway, I feel dumb not working it out myself, it's very simple and clever looking at it. Is there a name for this algorithm? Maybe the imperative version using a loop would be more familiar?

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  • Which is the most practical way to add functionality to this piece of code?

    - by Adam Arold
    I'm writing an open source library which handles hexagonal grids. It mainly revolves around the HexagonalGrid and the Hexagon class. There is a HexagonalGridBuilder class which builds the grid which contains Hexagon objects. What I'm trying to achieve is to enable the user to add arbitrary data to each Hexagon. The interface looks like this: public interface Hexagon extends Serializable { // ... other methods not important in this context <T> void setSatelliteData(T data); <T> T getSatelliteData(); } So far so good. I'm writing another class however named HexagonalGridCalculator which adds some fancy pieces of computation to the library like calculating the shortest path between two Hexagons or calculating the line of sight around a Hexagon. My problem is that for those I need the user to supply some data for the Hexagon objects like the cost of passing through a Hexagon, or a boolean flag indicating whether the object is transparent/passable or not. My question is how should I implement this? My first idea was to write an interface like this: public interface HexagonData { void setTransparent(boolean isTransparent); void setPassable(boolean isPassable); void setPassageCost(int cost); } and make the user implement it but then it came to my mind that if I add any other functionality later all code will break for those who are using the old interface. So my next idea is to add annotations like @PassageCost, @IsTransparent and @IsPassable which can be added to fields and when I'm doing the computation I can look for the annotations in the satelliteData supplied by the user. This looks flexible enough if I take into account the possibility of later changes but it uses reflection. I have no benchmark of the costs of using annotations so I'm a bit in the dark here. I think that in 90-95% of the cases the efficiency is not important since most users wont't use a grid where this is significant but I can imagine someone trying to create a grid with a size of 5.000.000.000 X 5.000.000.000. So which path should I start walking on? Or are there some better alternatives? Note: These ideas are not implemented yet so I did not pay too much attention to good names.

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  • Algorithm to infer tag hierarchy

    - by Tom
    I'm looking for an algorithm to infer a hierarchy from a set of tagged items. E.g. if the following items have the tags: 1 a 2 a,b 3 a,c 4 a,c,e 5 a,b 6 a,c 7 d 8 d,f Then I can construct an undirected graph (or graphs) by tallying the node weights and edge weights: node weights edge weights a 6 a-b 2 b 2 a-c 3 c 3 c-e 1 d 2 a-e 1 <-- this edge is parallel to a-c and c-e and not wanted e 1 d-f 1 f 1 The first problem is how to drop any redundant edges to get to the simplified graph? Note that it's only appropriate to remove that redundant a-e edge in this case because something is tagged as a-c-e, if that wasn't the case and the tag was a-e, that edge would have to remain. I suspect that means the removal of edges can only happen during the construction of the graph, not after everything has been tallied up. What I'd then like to do is identify the direction of the edges to create a directed graph (or graphs) and pick out root nodes to hopefully create a tree (or trees): trees a d // \\ | b c f \ e It seems like it could be a string algorithm - longest common subsequences/prefixes - or a tree/graph algorithm, but I am a little stuck since I don't know the correct terminology to search for it.

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