# Search Results

• ### Simplest possible voting/synchronization algorithm

##### - by Domchi
What would be a simplest algorithm one or more people could use to decide who of them should perform some task? There is one task, which needs to be done only once, and one or more people. People can speak, that is, send messages one to another. Communication must be minimal, and all people use the exact same algorithm. One person saying "I'm doing it" is not good enough since two persons may say it at a same time. Simplest that comes to my mind is that each person says a number and waits a bit. If somebody responds in that time, the person with lower number "wins" and does the task. If nobody responds, person says that she's doing it and does it. When she says that she does it, everybody else backs off. This should be enough to avoid two persons doing the task in the same time (since there is wait/handhake period), but might need a "second round" if both persons say the same number. Is there something simpler? For those curious, I'm trying to synchronize several copies of SecondLife LSL script to do something only once.

• ### Multiplication algorithm for abritrary precision (bignum) integers.

##### - by nn
Hi, I'm writing a small bignum library for a homework project. I am to implement Karatsuba multiplication, but before that I would like to write a naive multiplication routine. I'm following a guide written by Paul Zimmerman titled "Modern Computer Arithmetic" which is freely available online. On page 4, there is a description of an algorithm titled BasecaseMultiply which performs gradeschool multiplication. I understand step 2, 3, where B^j is a digit shift of 1, j times. But I don't understand step 1 and 3, where we have A*b_j. How is this multiplication meant to be carried out if the bignum multiplication hasn't been defined yet? Would the operation "*" in this algorithm just be the repeated addition method? Here is the parts I have written thus far. I have unit tested them so they appear to be correct for the most part: The structure I use for my bignum is as follows: #define BIGNUM_DIGITS 2048 typedef uint32_t u_hw; // halfword typedef uint64_t u_w; // word typedef struct { unsigned int sign; // 0 or 1 unsigned int n_digits; u_hw digits[BIGNUM_DIGITS]; } bn; Currently available routines: bn *bn_add(bn *a, bn *b); // returns a+b as a newly allocated bn void bn_lshift(bn *b, int d); // shifts d digits to the left, retains sign int bn_cmp(bn *a, bn *b); // returns 1 if a>b, 0 if a=b, -1 if a<b

• ### Algorithm to find the percentage of how much two texts are identical

##### - by qster
What algorithm would you suggest to identify how much from 0 to 1 (float) two texts are identical? Note that I don't mean similar (ie, they say the same thing but in a different way), I mean exact same words, but one of the two texts could have extra words or words slightly different or extra new lines and stuff like that. A good example of the algorithm I want is the one google uses to identify duplicate content in websites (X search results very similar to the ones shown have been omitted, click here to see them). The reason I need it is because my website has the ability for users to post comments; similar but different pages currently have their own comments, so many users ended up copy&pasting their comments on all the similar pages. Now I want to merge them (all similar pages will "share" the comments, and if you post it on page A it will appear on similar page B), and I would like to programatically erase all those copy&pasted comments from the same user. I have quite a few million comments but speed shouldn't be an issue since this is a one time thing that will run in the background. The programming language doesn't really matter (as long as it can interface to a MySQL database), but I was thinking of doing it in C++.

• ### algorithm || method to write prog

##### - by fatai
I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

• ### Algorithm possible amounts (over)paid for a specific price, based on denominations

##### - by Wrikken
In a current project, people can order goods delivered to their door and choose 'pay on delivery' as a payment option. To make sure the delivery guy has enough change customers are asked to input the amount they will pay (e.g. delivery is 48,13, they will pay with 60,- (3*20,-)). Now, if it were up to me I'd make it a free field, but apparantly higher-ups have decided is should be a selection based on available denominations, without giving amounts that would result in a set of denominations which could be smaller. Example: denominations = [1,2,5,10,20,50] price = 78.12 possibilities: 79 (multitude of options), 80 (e.g. 4*20) 90 (e.g. 50+2*20) 100 (2*50) It's international, so the denominations could change, and the algorithm should be based on that list. The closest I have come which seems to work is this: for all denominations in reversed order (large=>small) add ceil(price/denomination) * denomination to possibles baseprice = floor(price/denomination) * denomination; for all smaller denominations as subdenomination in reversed order add baseprice + (ceil((price - baseprice) / subdenomination) * subdenomination) to possibles end for end for remove doubles sort Is seems to work, but this has emerged after wildly trying all kinds of compact algorithms, and I cannot defend why it works, which could lead to some edge-case / new countries getting wrong options, and it does generate some serious amounts of doubles. As this is probably not a new problem, and Google et al. could not provide me with an answer save for loads of pages calculating how to make exact change, I thought I'd ask SO: have you solved this problem before? Which algorithm? Any proof it will always work?

• ### Algorithm(s) for rearranging simple symbolic algebraic expressions

##### - by Gabe Johnson
Hi, I would like to know if there is a straightforward algorithm for rearranging simple symbolic algebraic expressions. Ideally I would like to be able to rewrite any such expression with one variable alone on the left hand side. For example, given the input: m = (x + y) / 2 ... I would like to be able to ask about x in terms of m and y, or y in terms of x and m, and get these: x = 2*m - y y = 2*m - x Of course we've all done this algorithm on paper for years. But I was wondering if there was a name for it. It seems simple enough but if somebody has already cataloged the various "gotchas" it would make life easier. For my purposes I won't need it to handle quadratics. (And yes, CAS systems do this, and yes I know I could just use them as a library. I would like to avoid such a dependency in my application. I really would just like to know if there are named algorithms for approaching this problem.)

• ### Dynamic programming practice problems with solutions

##### - by Algorist
Hi, I have seen many questions on stackoverflow where dynamic programming technique can be used to make a exponential algorithm, a polynomial one. I have seen standard problems on dynamic programming. Is there a website or book that contains practice problems and solutions? Thanks Bala

• ### Image rotation algorithm

##### - by Stefano Driussi
I'm looking for an algorithm that rotates an image by some degrees (input). public Image rotateImage(Image image, int degrees) (Image instances could be replaced with int[] containing each pixel RGB values, My problem is that i need to implement it for a JavaME MIDP 2.0 project so i must use code runnable on JVM prior to version 1.5 Can anyone help me out with this ? EDIT: I forgot to mention that i don't have SVG APIs available and that i need a method to rotate by arbitrary degree other than 90 - 180- 270 Also, no java.awt.* packages are available on MIDP 2.0

• ### Algorithm for heat map?

##### - by eshan
I have a list of values each with latitude and longitude. I'm looking to create a translucent heatmap image to overlay on Google Maps. I know there are server side and flash based solutions already, but I want to build this in javascript using the canvas tag. However, I can't seem to find a concise description of the algorithm used to turn coordinates and values into a heatmap. Can anyone provide or link to one? Thanks.

• ### Simplest Algorithm for 2D Interpolation

##### - by Gayan
I have two shapes which are cross sections of a channel. I want to calculate the cross section of an intermediate point between the two defined points. What's the simplest algorithm to use in this situation? P.S. I came across several algorithms like natural neighbor and poisson which seemed complex. I'm looking for a simple solution which could be implemented quickly

• ### C# Algorithm to Tint a Color a Certain Percent

##### - by Josh Close
I have a color and I want get a tint of that color by a certain percent. So 100% is the color itself, 90% is a slightly lighter color, etc. Basically, it's like adding 10% of opacity to the color, if the color is on a white background. I need to convert the color into a hex HTML color value, so I don't want transparency. Is there an algorithm to get a tint of the System.Drawing.Color RGB value?

• ### Pseudo LRU tree algorithm.

##### - by patros
A lot of descriptions of Pseudo LRU algorithms involve using a binary search tree, and setting flags to "point away" from the node you're searching for every time you access the tree. This leads to a reasonable approximation of LRU. However, it seems from the descriptions that all of the nodes deemed LRU would be leaf nodes. Is there a pseudo-LRU algorithm that deals with a static tree that will still perform reasonably well, while determining that non-leaf nodes are suitable LRU candidates?

• ### Moon / Lunar Phase Algorithm

##### - by Scott Bailey
Does anyone know an algorithm to either calculate the moon phase or age on a given date or find the dates for new/full moons in a given year? Googling tells me the answer is in some Astronomy book, but I don't really want to buy a whole book when I only need a single page.

• ### Dijstra shortest path algorithm with edge cost.

##### - by Svisstack
Hello, I have a directed, positive weighted graph. Each edge have a cost of use. I have only A money, i want to calculate shortest paths with dijkstra algorithm, but sum of edges costs on route must be less or equal to A. I want to do this with most smallest Dijstra modification (if I can do it with small modification of Dijkstra). Anyone can help me with this?

• ### Algorithm for 2D Interpolation

##### - by Gayan
I have two shapes which are cross sections of a channel. I want to calculate the cross section of an intermediate point between the two defined points. What's the simplest algorithm to use in this situation? P.S. I came across several algorithms like natural neighbor and poisson which seemed complex. I'm looking for a simple solution which could be implemented quickly EDIT: I removed the word "Simplest" from the title since it might be misleading

• ### What are The opencv function useful for 2d skeleton estimation(ofRecursive centroids) [closed]

##### - by kumar
Possible Duplicate: Which is the best algorithm to “Estimate and Visulize 2d skeleton using Opencv” from the drawn contour Opencv functions or stepts for 2d skeleton estimation

• ### Neural Net Optimize w/ Genetic Algorithm

##### - by ServAce85
Is a genetic algorithm the most efficient way to optimize the number of hidden nodes and the amount of training done on an artificial neural network? I am coding neural networks using the NNToolbox in Matlab. I am open to any other suggestions of optimization techniques, but I'm most familiar with GA's.

• ### Graph spacing algorithm

##### - by David
Hi, I am looking for an algorithm that would be useful for determining x y coordinates for a number objects to display on screen. Each object can be related to another object and there can be any number of relationships and there can be any number of these objects. There is no restriction on the overall size of area on which to display these object. I am writing this in php and would be looking to store the coordinates in an array.

• ### Algorithm Analysis tool for java

##### - by Mansoor
I am looking for an algorithm analysis tool for java that can calculate Big 0 of a function. Ideal I would like to make it part of my build process, along side of my other code metrics tool. Even after searching on google I am unable to find any opensource of commercial tool. Any suggestion would be welcome Thanks

• ### Bezier Algoritms - an algorithm for inserting points

##### - by Sorush Rabiee
I'm looking for an algorithm to insert a new control point on a bezier curve, without deforming: did anybody knows a library or reference for bezier algorithms (insertion, optimize, de Casteljau ...)

• ### Word Anagram Hashing Algorithm?

##### - by Ahmed Said
Given set of words, we need to find the anagram words and display each category alone using the best algorithm input: man car kile arc none like output: man car arc kile like none the best solution I am developing now is based on a hashtable, but I am thinking about equation to convert anagram word into integer value exmaple: man = 'm'+'a'+'n' but this will not give unique values any suggestions?

• ### Psuedo LRU tree algorithm.

##### - by patros
A lot of descriptions of Pseudo LRU algorithms involve using a binary search tree, and setting flags to "point away" from the node you're searching for every time you access the tree. This leads to a reasonable approximation of LRU. However, it seems from the descriptions that all of the nodes deemed LRU would be leaf nodes. Is there a pseudo-LRU algorithm that deals with a static tree that will still perform reasonably well, while determining that non-leaf nodes are suitable LRU candidates?

• ### Algorithm putting point into square with maximal minimum distance

##### - by Mikulas Dite
I'm stuck on this: Have a square. Put n points into this square so the minimal distance (not necessary the average distance) is the highest possible. I'm looking for an algorithm which would be able to generate the coordinates of all points given the count of them. Example results for n=4;5;6: Please don't mention computing-power based stuff such as trying a lot of combination and then nitpicking the right one and similar ideas.

• ### aother option for modified preorder tree traversal algorithm

##### - by poldo
Hi, been searching for a while now and can't seem to find an alternative solution. I need the tree traversal algorithm in such a way that a node can have more than 1 parent, if it's possilbe (found a great article here: Storing Hierarchical Data in a Database). Are there any algorithms so that, starting from a root node, we can determine the sequence and dependencies of nodes (currently reading topological sorting)? thanks in advance!

• ### dijkstra/prim's algorithm...a little help?

##### - by bfpri
I was wondering for dijkstra's and prim's algorithm, what happens when they are choosing between more than one vertex to go to ,and there are more than one vertex with the same weight. For example