Search Results

Search found 4176 results on 168 pages for 'graph algorithms'.

Page 28/168 | < Previous Page | 24 25 26 27 28 29 30 31 32 33 34 35  | Next Page >

• Initialize array in amortized constant time -- what is this trick called?

  - by user946850

  There is this data structure that trades performance of array access against the need to iterate over it when clearing it. You keep a generation counter with each entry, and also a global generation counter. The "clear" operation increases the generation counter. On each access, you compare local vs. global generation counters; if they differ, the value is treated as "clean". This has come up in this answer on Stack Overflow recently, but I don't remember if this trick has an official name. Does it? One use case is Dijkstra's algorithm if only a tiny subset of the nodes has to be relaxed, and if this has to be done repeatedly.

  Read the article

• how to avoid or minimise use of check/conditional statement?

  - by Muneeb Nasir

  I have scenario, where i got stream and i need to check for some value. if i got my any new value i have to store it in any of data structure. well it seems very easy, i can place conditional statement if-else or can use contain method of set/map to check either received is new or not. but the problem is checking will effect my application performance, in stream i'll receive hundreds for value in second, if i start checking each and every value i received than for sure it effect performance. Any body can suggest me any mechanism or algorithm that solve my issue. either by bypassing checks or atleast minimize them?

  Read the article

• What is the name of this array transformation?

  - by Brandon Tilley

  Start with an array of arrays; in this case, they are different lengths in order to demonstrate the technique, but they do not have to be. [[1,2,3,4], [5,6,7], [8,9,10], [11,12,13,14,15]] At the other end of the transformation, you have an array of arrays where the first array contains the first element from each of the original arrays, the second array contains the second element from each of the original arrays, and so on. [[1,5,8,11], [2,6,9,12], [3,7,10,13], [4,14], [15]] Is there a mathematical or CS term for this operation?

  Read the article

• Randomization of biomes

  - by user24527

  You know how in Minecraft, the World is ever-expanding and all the biomes are randomized? My generalized question is: In relation to a space simulation that is also ever-expanding as the player moves about the world, how would one go about programming this randomization in Java? My real question is: Could I get a simplified example broken down into these example classes: astroids (This would include how many astroids there are, their positioning in space, their size, how often the larger astroids occur, how close they are to each other, the limitations of how many of the large asteroids can be in one field, how often astroid fields are generated, etc.) star-types (size, color, type, how often they occur, where hey occur, etc.) inhabitable-planets (size, positioning, how often they're generated, where they are generated, etc.) This would be very helpful currently since I wish to make a simplified version of such a program.

  Read the article

• Algorithm for grouping friends at the cinema [closed]

  - by Tim Skauge

  I got a brain teaser for you - it's not as simple as it sounds so please read and try to solve the issue. Before you ask if it's homework - it's not! I just wish to see if there's an elegant way of solving this. Here's the issue: X-number of friends want's to go to the cinema and wish to be seated in the best available groups. Best case is that everyone sits together and worst case is that everyone sits alone. Fewer groups are preferred over more groups. Sitting alone is least preferred. Input is the number of people going to the cinema and output should be an array of integer arrays that contains: Ordered combinations (most preferred are first) Number of people in each group Below are some examples of number of people going to the cinema and a list of preferred combinations these people can be seated: 1 person: 1 2 persons: 2, 1+1 3 persons: 3, 2+1, 1+1+1 4 persons: 4, 2+2, 3+1, 2+1+1, 1+1+1+1 5 persons: 5, 3+2, 4+1, 2+2+1, 3+1+1, 2+1+1+1, 1+1+1+1+1 6 persons: 6, 3+3, 4+2, 2+2+2, 5+1, 3+2+1, 2+2+1+1, 2+1+1+1+1, 1+1+1+1+1+1 Example with more than 7 persons explodes in combinations but I think you get the point by now. Question is: What does an algorithm look like that solves this problem? My language by choice is C# so if you could give an answer in C# it would be fantastic!

  Read the article

• What Is The Formula for the 3 of 9 Bar Code Alphabet?

  - by Chris Moschini

  Background: 3 of 9 Barcode Alphabet A simple syntax for 3 of 9 bar codes What is the formula behind the alphabet and digits in a 3 of 9 bar code? For example, ASCII has a relatively clear arrangement. Numbers start at 33, capitals at 65, lowercase at 97. From these starting points you can infer the ASCII code for any number or letter. The start point for each range is also a multiple of 32 + 1. Bar codes seem random and lacking sequence. If we use the syntax from the second link, this is the first six characters in 3 of 9: A 100-01 B 010-01 C 110-00 D 001-01 E 101-00 F 011-00 I see no pattern here; what is it? I'm as much interested in the designer's intended pattern behind these as I am in someone devising an algorithm of their own that can give you the above code for a given character based on its sequence. I struggled with where to put this question; is it history, computer science, information science? I chose Programmers because a StackExchange search had the most barcode hits here, and because I wanted to specifically relate it to ASCII to explain what sort of formula/explanation I'm looking for.

  Read the article

• How to create Button/Switch-Like Tile where you can step on it and change its value?

  - by aldroid16

  If the player steps on a Button-Tile when its true, it becomes false. If the player steps on a Button-Tile when it is false, it becomes true. The problem is, when the player stands on (intersects) the Button-Tile, it will keep updating the condition. So, from true, it becomes false. Because its false and the player intersects it, it becomes true again. True-false-true-false and so on. I use ElapsedGameTime to make the updating process slower, and the player can have a chance to change the Button to true or false. However, it's not the solution I was looking for. Is there any other way to make it keep in False/True condition while the Player is standing on the Button tile?

  Read the article

• How to avoid oscillation by async event based systems?

  - by inf3rno

  Imagine a system where there are data sources which need to be kept in sync. A simple example is model - view data binding by MVC. Now I intend to describe these kind of systems with data sources and hubs. Data sources are publishing and subscribing for events and hubs are relaying events to data sources. By handling an event a data source will change it state described in the event. By publishing an event the data source puts its current state to the event, so other data sources can use that information to change their state accordingly. The only problem with this system, that events can be reflected from the hub or from the other data sources, and that can put the system into an infinite oscillation (by async or infinite loop by sync). For example A -- data source B -- data source H -- hub A -> H -> A -- reflection from the hub A -> H -> B -> H -> A -- reflection from another data source By sync it is relatively easy to solve this issue. You can compare the current state with the event, and if they are equal, you don't change the state and raise the same event again. By async I could not find a solution yet. The state comparison does not work by async event handling because there is eventual consistency, and new events can be published in an inconsistent state causing the same oscillation. For example: A(*->x) -> H -> B(y->x) -- can go parallel with B(*->y) -> H -> A(x->y) -- so first A changes to x state while B changes to y state -- then B changes to x state while A changes to y state -- and so on for eternity... What do you think is there an algorithm to solve this problem? If there is a solution, is it possible to extend it to prevent oscillation caused by multiple hubs, multiple different events, etc... ? update: I don't think I can make this work without a lot of effort. I think this problem is just the same as we have by syncing multiple databases in a distributed system. So I think what I really need is constraints if I want to prevent this problem in an automatic way. What constraints do you suggest?

  Read the article

• Calculate pi to an accuracy of 5 decimal places?

  - by pgras

  In this message at point 18 I saw following programming question: Given that Pi can be estimated using the function 4 * (1 – 1/3 + 1/5 – 1/7 + …) with more terms giving greater accuracy, write a function that calculates Pi to an accuracy of 5 decimal places. So I know how to implement the given function and how to choose how "far" I should calculate, but how can I tell when I've reached the "accuracy of 5 decimal places" ?

  Read the article

• Removing ocurrances of characters in a string

  - by DmainEvent

  I am reading this book, programming Interviews exposed by John Wiley and sons and in chapter 6 they are discussing removing all instances of characters in a src string using a removal string... so removeChars(string str, string remove) In there writeup they sey the steps to accomplish this are to have a boolean lookup array with all values initially set to false, then loop through each character in remove setting the corresponding value in the lookup array to true (note: this could also be a hash if the possible character set where huge like Unicode-16 or something like that or if str and remove are both relatively small... < 100 characters I suppose). You then iterate through the str with a source and destination index, copying each character only if its corresponding value in the lookup array is false... Which makes sense... I don't understand the code that they use however... They have for(src = 0; src < len; ++src){ flags[r[src]] == true; } which is turning the flag value at the remove string indexed at src to true... so if you start out with PLEASE HELP as your str and LEA as your remove you will be setting in your flag table at 0,1,2... t|t|t but after that you will get an out of bounds exception because r doesn't have have anything greater than 2 in it... even using there example you get an out of bounds exception... Am is there code example unworkable?

  Read the article

• Find possible variations of one item out of multiple baskets.

  - by tugberk

  I have three baskets of balls and each of them has 10 balls which have the following numbers: Basket 1: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Basket 2: 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 Basket 3: 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 What would be the possible variations If I were to pick one ball from each basket? I guess this is called as Probability in Mathematics but not sure. How would you write this code in C# (or any other programming language) to get the correct results? Edit: Based on @Kilian Foth's comment, here is the solution in C#: class Program { static void Main(string[] args) { IEnumerable<string> basket1 = new List<string> { "1", "2", "3", "4", "5", "6", "7", "8", "9", "10" }; IEnumerable<string> basket2 = new List<string> { "11", "12", "13", "14", "15", "16", "17", "18", "19", "20" }; IEnumerable<string> basket3 = new List<string> { "21", "22", "23", "24", "25", "26", "27", "28", "29", "30" }; foreach (var item1 in basket1) foreach (var item2 in basket2) foreach (var item3 in basket3) { Console.WriteLine("{0}, {1}, {2}", item1, item2, item3); } Console.ReadLine(); } }

  Read the article

• Finding maximum number of congruent numbers

  - by Stefan Czarnecki

  Let's say we have a multiset (set with possible duplicates) of integers. We would like to find the size of the largest subset of the multiset such that all numbers in the subset are congruent to each other modulo some m 1. For example: 1 4 7 7 8 10 for m = 2 the subsets are: (1, 7, 7) and (4, 8, 10), both having size 3. for m = 3 the subsets are: (1, 4, 7, 7, 10) and (8), the larger set of size 5. for m = 4 the subsets are: (1), (4, 8), (7, 7), (10), the largest set of size 2. At this moment it is evident that the best answer is 5 for m = 3. Given m we can find the size of the largest subset in linear time. Because the answer is always equal or larger than half of the size of the set, it is enough to check for values of m upto median of the set. Also I noticed it is necessary to check for only prime values of m. However if values in the set are large the algorithm is still rather slow. Does anyone have any ideas how to improve it?

  Read the article

• Partitioning set into subsets with respect to equality of sum among subsets

  - by Al.Net

  let say i have {3, 1, 1, 2, 2, 1,5,2,7} set of numbers, I need to split the numbers such that sum of subset1 should be equal to sum of subset2 {3,2,7} {1,1,2,1,5,2}. First we should identify whether we can split number(one way might be dividable by 2 without any remainder) and if we can, we should write our algorithm two create s1 and s2 out of s. How to proceed with this approach? I read partition problem in wiki and even in some articles but i am not able to get anything. Can someone help me to find the right algorithm and its explanation in simple English?

  Read the article

• solve TOR edge node problem by using .onion proxy?

  - by rd.

  I would like to improve the TOR network, where the exit nodes are a vulnerability to concealing traffic. From my understanding, traffic to .onion sites are not decrypted by exit nodes, so therefore - in theory - a .onion site web proxy could be used to further anonymize traffic. Yes/no? perhaps you have insight into the coding and routing behind these concepts to elaborate on why this is a good/not good idea.

  Read the article

• Looking for a dynamic programming solution

  - by krammer

  Given a sequence of integers in range 1 to n. Each number can appear at most once. Let there be a symbol X in the sequence which means remove the minimum element from the list. There can be an arbitrarily number of X in the sequence. Example: 1,3,4,X,5,2,X The output is 1,2. We need to find the best way to perform this operation. The solution I have been thinking is: Scan the sequence from left to right and count number of X which takes O(n) time. Perform partial sorting and find the k smallest elements (k = number of X) which takes O(n+klogk) time using median of medians. Is there a better way to solve this problem using dynamic programming or any other way ?

  Read the article

• Help with a formula for Google Adwords [closed]

  - by XaviEsteve

  Hi guys, This question is more about maths and algorythms in Google Adwords but guess it's the most appropriate community in SE to ask this. I am creating a spreadsheet to calculate Adword formulas and I am stuck in how to calculate the Monthly Net Income for each keyword. I have created a formula which calculates it but can't figure out how to limit the Monthly Budget. The formula I've created is this one: Monthly Net Income = ( DailyClicks x ConversionRate x SaleProfit) - ( CPC x DailyClicks ) There is an example of the formula in the file which is a Google Spreadsheet publicly available here: https://spreadsheets.google.com/ccc?key=0AnQMyM9XJ0EidDB6TUF0OTdaZ2dFb2ZGNmhQeE5lb0E&hl=en_GB#gid=2 (you can create your own copy going to File Make a copy...) I am releasing this set of tools as Public Domain so feel free to use it :) Any help is much appreciated!

  Read the article

• Arranging the colors on the board in the most pleasing form

  - by Shashwat

  Given a rectangular board of height H and width W. N colors are given. ith color occupy Pi percentage of area on the board. Sum of Pis is 1. What can be algorithm to layout the colors on the board in the form of rectangles in the most pleasing form. By pleasing mean the aspect ratios (Width/Height) of rectangle of each color should be as close to 1 as possible. In an ideal case the board would be filled only with squares.

  Read the article

• reference list for non-IT driven algorithmic patterns

  - by Quicker

  I am looking for a reference list for non-IT driven algorithmic patterns (which still can be helped with IT implementations of IT). An Example List would be: name; short desc; reference Travelling Salesman; find the shortest possible route on a multiple target path; http://en.wikipedia.org/wiki/Travelling_salesman_problem Ressource Disposition (aka Regulation); Distribute a limited/exceeding input on a given number output receivers based on distribution rules; http://database-programmer.blogspot.de/2010/12/critical-analysis-of-algorithm-sproc.html If there is no such list, but you instantly think of something specific, please 'put it on the desk'. Maybe I can compile something out of the input I get here (actually I am very frustrated as I did not find any such list via research by myself). Details on Scoping: I found it very hard to formulate what I want in a way everything is out that I do not need (which may be the issue why I did not find anything at google). There is a database centric definition for what I am looking for in the section 'Processes' of the second example link. That somehow fits, but the database focus sort of drifts away from the pattern thinking, which I have in mind. So here are my own thoughts around what's in and what's out: I am NOT looking for a foundational algo ref list, which is implemented as basis for any programming language. Eg. the php reference describes substr and strlen. That implements algos, but is not what I am looking for. the problem the algo does address would even exist, if there were no computers (or other IT components) the main focus of the algo is NOT to help other algo's chances are high, that there are implementions of the solution or any workaround without any IT support out there in the world however the algo could be benefitialy implemented/fully supported by a software application = means: the problem of the algo has to be addressed anyway, but running an algo implementation with software automates the process (that is why I posted it on stackoverflow and not somewhere else) typically such algo implementations have more than one input field value and more than one output field value - which implies it could not be implemented as simple function (which is fixed to produce not more than one output value) in a normalized data model often times such algo implementation outputs span accross multiple rows (sometimes multiple tables), whereby the number of output rows depends on the input paraters and rows in the table(s) at start time - which implies that any algo implementation/procedure must interact with a database (read and/or write) I am mainly looking for patterns, not for specific implementations. Example: The Travelling Salesman assumes any coordinates, however it does not say: You need a table targets with fields x and y. - however sometimes descriptions are focussed on examples with specific implementations very much - no worries, as long as the pattern gets clear

  Read the article

• Where would you start if you were trying to solve this PDF classification problem?

  - by burtonic

  We are crawling and downloading lots of companies' PDFs and trying to pick out the ones that are Annual Reports. Such reports can be downloaded from most companies' investor-relations pages. The PDFs are scanned and the database is populated with, among other things, the: Title Contents (full text) Page count Word count Orientation First line Using this data we are checking for the obvious phrases such as: Annual report Financial statement Quarterly report Interim report Then recording the frequency of these phrases and others. So far we have around 350,000 PDFs to scan and a training set of 4,000 documents that have been manually classified as either a report or not. We are experimenting with a number of different approaches including Bayesian classifiers and weighting the different factors available. We are building the classifier in Ruby. My question is: if you were thinking about this problem, where would you start?

  Read the article

• Grid Game Algorithm

  - by 7Aces

  Problem Link - http://www.iarcs.org.in/inoi/2009/zco2009/zco2009-1a.php You have to find the path with the maximum weight, from the top-left cell to the bottom-right cell. It could've been solved with a simple Dynamic Programming approach, if it were not for the special condition - you are allowed at most one move that can be either to the left or up. How do I now approach the problem with this special case? Also, I'm looking for a time-efficient approach. Thanks!

  Read the article

• Algorithm for optimal combination of two variables

  - by AlanChavez

  I'm looking for an algorithm that would be able to determine the optimal combination of two variables, but I'm not sure where to start looking. For example, if I have 10,000 rows in a database and each row contains price, and square feet is there any algorithm out there that will be able to determine what combination of price and sq ft is optimal. I know this is vague, but I assume is along the lines of Fuzzy logic and fuzzy sets, but I'm not sure and I'd like to start digging in the right field to see if I can come up with something that solves my problem.

  Read the article

• Is the Leptonica implementation of 'Modified Median Cut' not using the median at all?

  - by TheCodeJunkie

  I'm playing around a bit with image processing and decided to read up on how color quantization worked and after a bit of reading I found the Modified Median Cut Quantization algorithm. I've been reading the code of the C implementation in Leptonica library and came across something I thought was a bit odd. Now I want to stress that I am far from an expert in this area, not am I a math-head, so I am predicting that this all comes down to me not understanding all of it and not that the implementation of the algorithm is wrong at all. The algorithm states that the vbox should be split along the lagest axis and that it should be split using the following logic The largest axis is divided by locating the bin with the median pixel (by population), selecting the longer side, and dividing in the center of that side. We could have simply put the bin with the median pixel in the shorter side, but in the early stages of subdivision, this tends to put low density clusters (that are not considered in the subdivision) in the same vbox as part of a high density cluster that will outvote it in median vbox color, even with future median-based subdivisions. The algorithm used here is particularly important in early subdivisions, and 3is useful for giving visible but low population color clusters their own vbox. This has little effect on the subdivision of high density clusters, which ultimately will have roughly equal population in their vboxes. For the sake of the argument, let's assume that we have a vbox that we are in the process of splitting and that the red axis is the largest. In the Leptonica algorithm, on line 01297, the code appears to do the following Iterate over all the possible green and blue variations of the red color For each iteration it adds to the total number of pixels (population) it's found along the red axis For each red color it sum up the population of the current red and the previous ones, thus storing an accumulated value, for each red note: when I say 'red' I mean each point along the axis that is covered by the iteration, the actual color may not be red but contains a certain amount of red So for the sake of illustration, assume we have 9 "bins" along the red axis and that they have the following populations 4 8 20 16 1 9 12 8 8 After the iteration of all red bins, the partialsum array will contain the following count for the bins mentioned above 4 12 32 48 49 58 70 78 86 And total would have a value of 86 Once that's done it's time to perform the actual median cut and for the red axis this is performed on line 01346 It iterates over bins and check they accumulated sum. And here's the part that throws me of from the description of the algorithm. It looks for the first bin that has a value that is greater than total/2 Wouldn't total/2 mean that it is looking for a bin that has a value that is greater than the average value and not the median ? The median for the above bins would be 49 The use of 43 or 49 could potentially have a huge impact on how the boxes are split, even though the algorithm then proceeds by moving to the center of the larger side of where the matched value was.. Another thing that puzzles me a bit is that the paper specified that the bin with the median value should be located, but does not mention how to proceed if there are an even number of bins.. the median would be the result of (a+b)/2 and it's not guaranteed that any of the bins contains that population count. So this is what makes me thing that there are some approximations going on that are negligible because of how the split actually takes part at the center of the larger side of the selected bin. Sorry if it got a bit long winded, but I wanted to be as thoroughas I could because it's been driving me nuts for a couple of days now ;)

  Read the article

• How should I compress a file with multiple bytes that are the same with Huffman coding?

  - by Omega

  On my great quest for compressing/decompressing files with a Java implementation of Huffman coding (http://en.wikipedia.org/wiki/Huffman_coding) for a school assignment, I am now at the point of building a list of prefix codes. Such codes are used when decompressing a file. Basically, the code is made of zeroes and ones, that are used to follow a path in a Huffman tree (left or right) for, ultimately, finding a byte. In this Wikipedia image, to reach the character m the prefix code would be 0111 The idea is that when you compress the file, you will basically convert all the bytes of the file into prefix codes instead (they tend to be smaller than 8 bits, so there's some gain). So every time the character m appears in a file (which in binary is actually 1101101), it will be replaced by 0111 (if we used the tree above). Therefore, 1101101110110111011011101101 becomes 0111011101110111 in the compressed file. I'm okay with that. But what if the following happens: In the file to be compressed there exists only one unique byte, say 1101101. There are 1000 of such byte. Technically, the prefix code of such byte would be... none, because there is no path to follow, right? I mean, there is only one unique byte anyway, so the tree has just one node. Therefore, if the prefix code is none, I would not be able to write the prefix code in the compressed file, because, well, there is nothing to write. Which brings this problem: how would I compress/decompress such file if it is impossible to write a prefix code when compressing? (using Huffman coding, due to the school assignment's rules) This tutorial seems to explain a bit better about prefix codes: http://www.cprogramming.com/tutorial/computersciencetheory/huffman.html but doesn't seem to address this issue either.

  Read the article

• Is using build-in sorting considered cheating in practice tests?

  - by user10326

  I am using one of the practice online judges where a practice problem is asked and one submits the answer and gets back if it is accepted or not based on test inputs. My question is the following: In one of the practice tests, I needed to sort an array as part of the solution algorithm. If it matters the problem was: find 2 numbers in an array that add up to a specific target. As part of my algorithm I sorted the array, but to do that I used Java's quicksort and not implement sorting as part of the same method. To do that I had to do: java.util.Arrays.sort(array); Since I had to use the fully qualified name I am wondering if this is a kind of "cheating". (I mean perhaps an online judge does not expect this) Is it? In a formal interview (since these tests are practice for interview as I understand) would this be acceptable?

  Read the article

• Is there a phrase or word to describe an algorithim or program is complete in that given any value for its arguments there is a defined outcome?

  - by Mrk Mnl

  Is there a phrase or word to describe an algorithim or programme is complete in that given any value for its arguments there is a defined outcome? i.e. all the ramifications have been considered whatever the context? A simple example would be the below function: function returns string get_item_type(int type_no) { if(type_no < 10) return "hockey stick" else if (type_no < 20) return "bulldozer" else return "unknown" } (excuse the dismal pseudo code) No matter what number is supplied all possibiblites are catered for. My question is: is there a word to fill the blank here: "get_item_type() is ______ complete" ? (The answer is not Turing Complete - that is something quite different - but I annoyingly always think of something as "Turing Complete" when I am thinking of the above).

  Read the article

< Previous Page | 24 25 26 27 28 29 30 31 32 33 34 35  | Next Page >