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• Finding anagaram(s) of dictionary words

  - by Codenotguru

  How can I take an input word (or sequence of letters) and output a word from a dictionary that contains exactly those letters? Does java has an English dictionary class (list of words) that I can use, or are there open source implementations of this? How can I optimize my code if this needs to be done repeatedly?

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• How to Zip one IEnumerable with itself

  - by wageoghe

  I am implementing some math algorithms based on lists of points, like Distance, Area, Centroid, etc. Just like in this post: http://stackoverflow.com/questions/2227828/find-the-distance-required-to-navigate-a-list-of-points-using-linq That post describes how to calculate the total distance of a sequence of points (taken in order) by essentially zipping the sequence "with itself", generating the sequence for Zip by offsetting the start position of the original IEnumerable by 1. So, given the Zip extension in .Net 4.0, assuming Point for the point type, and a reasonable Distance formula, you can make calls like this to generate a sequence of distances from one point to the next and then to sum the distances: var distances = points.Zip(points.Skip(1),Distance); double totalDistance = distances.Sum(); Area and Centroid calculations are similar in that they need to iterate over the sequence, processing each pair of points (points[i] and points[i+1]). I thought of making a generic IEnumerable extension suitable for implementing these (and possibly other) algorithms that operate over sequences, taking two items at a time (points[0] and points[1], points[1] and points[2], ..., points[n-1] and points[n] (or is it n-2 and n-1 ...) and applying a function. My generic iterator would have a similar signature to Zip, but it would not receive a second sequence to zip with as it is really just going to zip with itself. My first try looks like this: public static IEnumerable<TResult> ZipMyself<TSequence, TResult>(this IEnumerable<TSequence> seq, Func<TSequence, TSequence, TResult> resultSelector) { return seq.Zip(seq.Skip(1),resultSelector); } With my generic iterator in place, I can write functions like this: public static double Length(this IEnumerable<Point> points) { return points.ZipMyself(Distance).Sum(); } and call it like this: double d = points.Length(); and double GreensTheorem(Point p1, Point p1) { return p1.X * p2.Y - p1.Y * p2.X; } public static double SignedArea(this IEnumerable<Point> points) { return points.ZipMyself(GreensTheorem).Sum() / 2.0 } public static double Area(this IEnumerable<Point> points) { return Math.Abs(points.SignedArea()); } public static bool IsClockwise(this IEnumerable<Point> points) { return SignedArea(points) < 0; } and call them like this: double a = points.Area(); bool isClockwise = points.IsClockwise(); In this case, is there any reason NOT to implement "ZipMyself" in terms of Zip and Skip(1)? Is there already something in LINQ that automates this (zipping a list with itself) - not that it needs to be made that much easier ;-) Also, is there better name for the extension that might reflect that it is a well-known pattern (if, indeed it is a well-known pattern)? Had a link here for a StackOverflow question about area calculation. It is question 2432428. Also had a link to Wikipedia article on Centroid. Just go to Wikipedia and search for Centroid if interested. Just starting out, so don't have enough rep to post more than one link,

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• commands&creating pointer [closed]

  - by gcc

  input 23 3 4 4 42 n 23 0 9 9 n n n 3 9 9 x //according to input,i should create int pointer arrays. pointer arrays // starting from 1 (that is initial arrays is arrays[1].when program sees n ,it // must be jumb to arrays 2 // the first int input 23 is num_arrays which used in malloc(sizeof(int)*num_arrays expected output: elements of arrays[1] 3 4 5 42 elements of arrays[2] 23 0 9 9 elements of arrays[5] 3 9 9 another input 12 2 3 4 n n 2 3 4 n 12 3 x expected output elements of arrays[1] 2 3 4 elements of arrays[3] 2 3 4 elements of arrays[4] 12 3 specification: x is stopper n is comman to create new pointer array i am new in this site anyone help me how can i write

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• Singleton design pattern vs Singleton beans in Spring container

  - by Peeyush

  As we all know we have beans as singleton by default in Spring container and if we have a web application based on Spring framework then in that case do we really need to implement Singleton design pattern to hold global data rather than just creating a bean through spring. Please bear with me if I'm not able to explain what I actually meant to ask.

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• Looking for more details about "Group varint encoding/decoding" presented in Jeff's slides

  - by Mickey Shine

  I noticed that in Jeff's slides "Challenges in Building Large-Scale Information Retrieval Systems", which can also be downloaded here: http://research.google.com/people/jeff/WSDM09-keynote.pdf, a method of integers compression called "group varint encoding" was mentioned. It was said much faster than 7 bits per byte integer encoding (2X more). I am very interested in this and looking for an implementation of this, or any more details that could help me implement this by myself. I am not a pro and new to this, and any help is welcome!

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• Find largest rectangle containing all zero's in an N X N binary matrix

  - by Rajendra

  Given an N X N binary matrix (containing only 0's or 1's). How can we go about finding largest rectangle containing all 0's? Example: I 0 0 0 0 1 0 0 0 1 0 0 1 II->0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 <--IV 0 0 1 0 0 0 IV is a 6 X 6 binary matrix, return value in this case will be Cell 1: (2, 1) and Cell 2: (4, 4). Resulting sub-matrix can be square or rectangle. Return value can be size of the largest sub-matrix of all 0's also, for example, here 3 X 4.

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• How is counting sort a stable sort?

  - by eSKay

  Suppose my input is (a,b and c to distinguish between equal keys) 1 6a 8 3 6b 0 6c 4 My counting sort will save as (discarding the a,b and c info!!) 0(1) 1(1) 3(1) 4(1) 6(3) 8(1) which will give me the result 0 1 3 4 6 6 6 8 So, how is this stable sort? I am not sure how it is "maintaining the relative order of records with equal keys." Please explain.

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• Single Table Inheritance (Database Inheritance design options) pros and cons and in which case it us

  - by Yosef

  Hi, I study about today about 2 database design inheritance approaches: 1. Single Table Inheritance 2. Class Table Inheritance In my student opinion Single Table Inheritance make database more smaller vs other approaches because she use only 1 table. But i read that the more favorite approach is Class Table Inheritance according Bill Karwin. My Question is: Single Table Inheritance pros and cons and in which case it used? thanks, Yosef

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• n & x commands&creating pointer&with using malloc [closed]

  - by gcc

  input 23 3 4 4 42 n 23 0 9 9 n n n 3 9 9 x //according to input,i should create int pointer arrays. pointer arrays // starting from 1 (that is initial arrays is arrays[1].when program sees n ,it // must be jumb to arrays 2 // the first int input 23 is num_arrays which used in malloc(sizeof(int)*num_arrays expected output arrays[1] 3 4 5 42 arrays[2] 23 0 9 9 arrays[5] 3 9 9 another input 12 2 3 4 n n 2 3 4 n 12 3 x expected output arrays[1] 2 3 4 arrays[3] 2 3 4 arrays[4] 12 3 x is stopper n is comman to create new pointer array i am new in this site anyone help me how can i write

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• Programming language shootout: code most like pseudocode for Dijkstra's Algorithm

  - by Casebash

  Okay, so this question here asked which language is most like executable pseudocode, so why not find out by actually writing some code! Here we have a competition where I will award a 100 point bounty (I know its not much, but I am poor after the recalc) to the code which most resembles this pseudocode. I've read through this a few times so I'm pretty sure that this pseudocode below is correct and about as unambiguous as pseudocode can be. Personally, I'm going to have a go in Python and probably Haskell as well, but I'm just learning the later so my attempt will probably be pretty poor. Note: Obviously to implement anything looking like this you'll have to define quite a few library functions. define DirectedGraph G with: Vertices as V, Edges as E define Vertex A, Z declare each e in E as having properties: Boolean fixed with: initial=false Real minSoFar with: initial=0 for A else infinity define PriorityQueue pq with: objects=V initial=A priority v=v.minSoFar create triggers for v in V: when v.minSoFar event reduced then pq.addOrUpdate v when v.fixed event becomesTrue then pq.remove v Repeat until Z.fixed==True: define Vertex U=pq.pop() U.fixed=True for Edge E adjacentTo U with other Vertex V: V.minSoFar=U.minSoFar+length(E) if reducesValue return Z.name, Z.minSoFar

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• reopen or read and say why not reopened [closed]

  - by gcc

  input 23 3 4 4 42 n 23 0 9 9 n n n 3 9 9 x //according to input,i should create int pointer arrays. pointer arrays // starting from 1 (that is initial arrays is arrays[1].when program sees n ,it // must be jumb to arrays 2 // the first int input 23 is num_arrays which used in malloc(sizeof(int)*num_arrays expected output: elements of arrays[1] 3 4 5 42 elements of arrays[2] 23 0 9 9 elements of arrays[5] 3 9 9 another input 12 2 3 4 n n 2 3 4 n 12 3 x expected output elements of arrays[1] 2 3 4 elements of arrays[3] 2 3 4 elements of arrays[4] 12 3 specification: x is stopper n is comman to create new pointer array i am new in this site anyone help me how can i write

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• Sha or Md5 algorithm i need to encrypt and decrypt in flex

  - by praveen

  Hi I am developing my application in flex and JSP, so when I am passing values through HTTP Service Post method with request object but these values are tracing and modifying by testing team so I am planning to encrypt values in flex and decrypt it in jsp.so is there any algorithms like SHA or MD5 more secure algorithms, so please send any code or related links it is very useful to me. I am using like httpService = new HTTPService; httpService.request = new Object; httpService.request.task = "doInvite"; httpService.request.email = emailInput.text; httpService.request.firstName = firstNameInput.text; httpService.request.lastName = lastNameInput.text; httpService.send(); So is there any other way to give more secure ,please help me in this,Thanks in Advance.

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• Using logarithms to normalize a vector to avoid overflow

  - by muscicapa

  http://stackoverflow.com/questions/2293762/problem-with-arithmetic-using-logarithms-to-avoid-numerical-underflow-take-2 Having seen the above and having seen softmax normalization I was trying to normalize a vector while avoiding overflow - that is (x1 x2 x3 x4 ... xn) the normalized form for me has the sum of squares as 1.0 So what I thought of doing is s=(2*log(x1)+2*log(x2)+...+2*log(xn))/2 so the two factor can be taken off and finally the normalized vector is exp(log(x1)-s), , ..., exp(log(xn)-s) but I am evidently doing something wrong here, what?

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• C# average function for large numbers without overflow exception

  - by Ron Klein

  .NET Framework 3.5. I'm trying to calculate the average of some pretty large numbers. For instance: using System; using System.Linq; class Program { static void Main(string[] args) { var items = new long[] { long.MaxValue - 100, long.MaxValue - 200, long.MaxValue - 300 }; try { var avg = items.Average(); Console.WriteLine(avg); } catch (OverflowException ex) { Console.WriteLine("can't calculate that!"); } Console.ReadLine(); } } Obviously, the mathematical result is 9223372036854775607 (long.MaxValue - 200), but I get an exception there. This is because the implementation (on my machine) to the Average extension method, as inspected by .NET Reflector is: public static double Average(this IEnumerable<long> source) { if (source == null) { throw Error.ArgumentNull("source"); } long num = 0L; long num2 = 0L; foreach (long num3 in source) { num += num3; num2 += 1L; } if (num2 <= 0L) { throw Error.NoElements(); } return (((double) num) / ((double) num2)); } I know I can use a BigInt library (yes, I know that it is included in .NET Framework 4.0, but I'm tied to 3.5). But I still wonder if there's a pretty straight forward implementation of calculating the average of integers without an external library. Do you happen to know about such implementation? Thanks!!

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• What problems have you solved using artificial neural networks?

  - by knorv

  I'd like to know about specific problems you - the SO reader - have solved using artificial neural network techniques and what libraries/frameworks you used if you didn't roll your own. Questions: What problems have you used artificial neural networks to solve? What libraries/frameworks did you use? I'm looking for first-hand experiences, so please do not answer unless you have that.

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• C# rounding DateTime objects

  - by grenade

  I want to round dates/times to the nearest interval for a charting application. I'd like an extension method signature like follows so that the rounding can be acheived for any level of accuracy: static DateTime Round(this DateTime date, TimeSpan span); The idea is that if I pass in a timespan of ten minutes, it will round to the nearest ten minute interval. I can't get my head around the implementation and am hoping one of you will have written or used something similar before. I think either a floor, ceiling or nearest implementation is fine. Any ideas? Edit: Thanks to @tvanfosson & @ShuggyCoUk, the implementation looks like this: public static class DateExtensions { public static DateTime Round(this DateTime date, TimeSpan span) { long ticks = (date.Ticks / span.Ticks) + (span.Ticks / 2) + 1; return new DateTime(ticks * span.Ticks); } public static DateTime Floor(this DateTime date, TimeSpan span) { long ticks = (date.Ticks / span.Ticks); return new DateTime(ticks * span.Ticks); } public static DateTime Ceil(this DateTime date, TimeSpan span) { long ticks = (date.Ticks + span.Ticks - 1) / span.Ticks; return new DateTime(ticks * span.Ticks); } } And is called like so: DateTime nearestHour = DateTime.Now.Round(new TimeSpan(1,0,0)); DateTime minuteCeiling = DateTime.Now.Ceil(new TimeSpan(0,1,0)); DateTime weekFloor = DateTime.Now.Floor(new TimeSpan(7,0,0,0)); ... Cheers!

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• Quick Sort Vs Merge Sort

  - by Ganesh M

  Why might quick sort be better than merge sort ?

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• How do I convert decimal numbers to binary in Perl?

  - by David

  I am trying to make a program that converts decimal numbers or text into binary numbers in perl. The program asks for user input of a character or string , and then prints out the result to the console. How do I do this? My code I have been working on is below, but i cannot seem to fix it. print "Enter a number to convert: "; chomp($decimal = <STDIN>); print "\nConverting $number to binary...\n"; $remainder = $decimal%2; while($decimal > 0) { $decimal/2; print $remainder; }

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• Which data structure used in MySql?

  - by SomeUser

  Which data structure used in MySql?

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• C# average function without overflow exception

  - by Ron Klein

  .NET Framework 3.5. I'm trying to calculate the average of some pretty large numbers. For instance: using System; using System.Linq; class Program { static void Main(string[] args) { var items = new long[] { long.MaxValue - 100, long.MaxValue - 200, long.MaxValue - 300 }; try { var avg = items.Average(); Console.WriteLine(avg); } catch (OverflowException ex) { Console.WriteLine("can't calculate that!"); } Console.ReadLine(); } } Obviously, the mathematical result is 9223372036854775607 (long.MaxValue - 200), but I get an exception there. This is because the implementation (on my machine) to the Average extension method, as inspected by .NET Reflector is: public static double Average(this IEnumerable<long> source) { if (source == null) { throw Error.ArgumentNull("source"); } long num = 0L; long num2 = 0L; foreach (long num3 in source) { num += num3; num2 += 1L; } if (num2 <= 0L) { throw Error.NoElements(); } return (((double) num) / ((double) num2)); } I know I can use a BigInt library (yes, I know that it is included in .NET Framework 4.0, but I'm tied to 3.5). But I still wonder if there's a pretty straight forward implementation of calculating the average of integers without an external library. Do you happen to know about such implementation? Thanks!! UPDATE: The previous example, of three large integers, was just an example to illustrate the overflow issue. The question is about calculating an average of any set of numbers which might sum to a large number that exceeds the type's max value. Sorry about this confusion. I also changed the question's title to avoid additional confusion. Thanks all!!

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• about Randomized-select algorithm

  - by matin1234

  Hi I have this array A = <3,2,9,0,7,5,4,8,6,1> and I want to write all its worst partitions are these correct?thanks a1 = <0,2,9,3,7,5,4,8,6,1> a2 = <1,9,3,7,5,4,8,6,2> a3 = <2,3,7,5,4,8,6,9> a4 = <3,7,5,4,8,6,9> a5 = <4,5,7,8,6,9> a6 = <5,7,8,6,9> a7 = <6,8,7,9> a8 = <7,8,9> a9 = <8,9> a10 = <9>

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• Finding if a Binary Tree is a Binary Search Tree

  - by dharam

  Today I had an interview where I was asked to write a program which takes a Binary Tree and returns true if it is also a Binary Search Tree otherwise false. My Approach1: Perform an inroder traversal and store the elements in O(n) time. Now scan through the array/list of elements and check if element at ith index is greater than element at (i+1)th index. If such a condition is encountered, return false and break out of the loop. (This takes O(n) time). At the end return true. But this gentleman wanted me to provide an efficient solution. I tried but I was unsuccessfult, because to find if it is a BST I have to check each node. Moreover he was pointing me to think over recusrion. My Approach 2: A BT is a BST if for any node N N-left is < N and N-right N , and the INorder successor of left node of N is less than N and the inorder successor of right node of N is greater than N and the left and right subtrees are BSTs. But this is going to be complicated and running time doesn't seem to be good. Please help if you know any optimal solution. Thanks.

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• Software tools to automatically decrypt a file, whose encryption algorithm (and/or encryption keys)

  - by Andrew

  I have an idea for encryption that I could program fairly easily to encrypt some local text file. Given that my approach is novel, and does not use any of the industry standard encryption techniques, would I be able to test the strength of my encryption using 'cracker' apps or suchlike? Or do all those tools rely on advanced knowledge of the encryption process (or intercepted 'keys'), meaning I'd have to build my own cracker for testing?

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• Is there a website to lookup common, already written functions?

  - by pinnacler

  I'm sitting here writing a function that I'm positive has been written before, somewhere on earth. It's just too common to have not been attempted, and I'm wondering why I can't just go to a website and search for a function that I can then copy and paste into my project in 2 seconds, instead of wasting my day reinventing the wheel. Sure there are certain libraries you can use, but where do you find these libraries and when they are absent, is there a site like I'm describing? Possibly a wiki of some type that contains free code that anybody can edit and improve?

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• nth ugly number

  - by Anil Katti

  Numbers whose only prime factors are 2, 3 or 5 are called ugly numbers. Example: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, ... 1 can be considered as 2^0. I am working on finding nth ugly number. Note that these numbers are extremely sparsely distributed as n gets large. I wrote a trivial program that computes if a given number is ugly or not. For n 500 - it became super slow. I tried using memoization - observation: ugly_number * 2, ugly_number * 3, ugly_number * 5 are all ugly. Even with that it is slow. I tried using some properties of log - since that will reduce this problem from multiplication to addition - but, not much luck yet. Thought of sharing this with you all. Any interesting ideas? Using a concept similar to "Sieve of Eratosthenes" (thanks Anon) for (int i(2), uglyCount(0); ; i++) { if (i % 2 == 0) continue; if (i % 3 == 0) continue; if (i % 5 == 0) continue; uglyCount++; if (uglyCount == n - 1) break; } i is the nth ugly number. Even this is pretty slow. I am trying to find 1500th ugly number.

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