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  • C# - Google like query engine.-

    - by MRFerocius
    Guys; Hope you are fine. I have to make a Web Project (very simple) I will have a DB with 2 tables. One table has 2 fields. From the WebPage I need a Google like search query, for example I have Movie Title and Movie Review on the Table. I need to be able to search those 2 fields like this: "Best Movie" + Action I will need to make a query to the DB to search for the "Best Movie" string togheter plus optional ACTION word on 2 fields of the table. Am I clear??? :) Does somebody know if this has already been made, and if it´s public and free and where to get it :) Thanks in advanced EDIT: My concern is to translate the Google like Symbols ("", +, -, ~) to build a valid query.

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  • STL map--> sort by value?

    - by Charlie Epps
    Hi I wonder how can I implement the STL map sorting by value. For example, I have a map m map<int, int>; m[1] = 10; m[2] = 5; m[4] = 6; m[6] = 1; and then.. I'd like to sort that with the m's value. So, if I print the map, I'd like to get the result like m[6] = 1 m[2] = 5 m[4] = 6 m[1] = 10 this. How can I sort like this way? Is there any way that I can deal with the key and value with sorted values?

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  • Given 4 objects, how to figure out whether exactly 2 have a certain property

    - by Cocorico
    Hi guys! I have another question on how to make most elegant solution to this problem, since I cannot afford to go to computer school right so my actual "pure programming" CS knowledge is not perfect or great. This is basically an algorhythm problem (someone please correct me if I am using that wrong, since I don't want to keep saying them and embarass myself) I have 4 objects. Each of them has an species property that can either be a dog, cat, pig or monkey. So a sample situation could be: object1.species=pig object2.species=cat object3.species=pig object4.species=dog Now, if I want to figure out if all 4 are the same species, I know I could just say: if ( (object1.species==object2.species) && (object2.species==object3.species) && (object3.species==object4.species) ) { // They are all the same animal (don't care WHICH animal they are) } But that isn't so elegant right? And if I suddenly want to know if EXACTLY 3 or 2 of them are the same species (don't care WHICH species it is though), suddenly I'm in spaghetti code. I am using Objective C although I don't know if that matters really, since the most elegant solution to this is I assume the same in all languages conceptually? Anyone got good idea? Thanks!!

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  • Is it possible to create thread-safe collections without locks?

    - by Andrey
    This is pure just for interest question, any sort of questions are welcome. So is it possible to create thread-safe collections without any locks? By locks I mean any thread synchronization mechanisms, including Mutex, Semaphore, and even Interlocked, all of them. Is it possible at user level, without calling system functions? Ok, may be implementation is not effective, i am interested in theoretical possibility. If not what is the minimum means to do it? EDIT: Why immutable collections don't work. This of class Stack with methods Add that returns another Stack. Now here is program: Stack stack = new ...; ThreadedMethod() { loop { //Do the loop stack = stack.Add(element); } } this expression stack = stack.Add(element) is not atomic, and you can overwrite new stack from other thread. Thanks, Andrey

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  • Number of different elements in an array.

    - by AB
    Is it possible to compute the number of different elements in an array in linear time and constant space? Let us say it's an array of long integers, and you can not allocate an array of length sizeof(long). P.S. Not homework, just curious. I've got a book that sort of implies that it is possible.

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  • problem with evolutionary algorithms degrading into simulated annealing: mutation too small?

    - by Schnalle
    i have a problem understanding evolutionary algorithms. i tried using this technique several times, but i always ran into the same problem: degeneration into simulated annealing. lets say my initial population, with fitness in brackets, is: A (7), B (9), C (14), D (19) after mating and mutation i have following children: AB (8.3), AC (12.2), AD (14.1), BC(11), BD (14.7), CD (17) after elimination of the weakest, we get A, AB, B, AC next turn, AB will mate again with a result around 8, pushing AC out. next turn, AB again, pushing B out (assuming mutation changes fitness mostly in the 1 range). now, after only a few turns the pool is populated with the originally fittest candidates (A, B) and mutations of those two (AB). this happens regardless of the size of the initial pool, it just takes a bit longer. say, with an initial population of 50 it takes 50 turns, then all others are eliminated, turning the whole setup in a more complicated simulated annealing. in the beginning i also mated canditates with themselves, worsening the problem. so, what do i miss? are my mutation rates simply too small and will it go away if i increase them? here's the project i'm using it for: http://stefan.schallerl.com/simuan-grid-grad/ yeah, the code is buggy and the interface sucks, but i'm too lazy to fix it right now - and be careful, it may lock up your browser. better use chrome, even thought firefox is not slower than chrome for once (probably the tracing for the image comparison pays off, yay!). if anyone is interested, the code can be found here. here i just dropped the ev-alg idea and went for simulated annealing. ps: i'm not even sure about simulated annealing - it is like evolutionary algorithms, just with a population size of one, right?

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  • Finding a small image in a bigger one

    - by tur1ng
    Given an image with a large dimension ( 1.000 x 1.000). What is a good approach to find a small image (e.g. 50 x 50) in the big one? The smaller image can be rotated and differ in the size, but only with a 1:1 ratio. It's not related to any programming language - I'm just interested in pattern recognition. Thank you.

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  • How to calculate this string-dissimilarity function efficiently?

    - by ybungalobill
    Hello, I was looking for a string metric that have the property that moving around large blocks in a string won't affect the distance so much. So "helloworld" is close to "worldhello". Obviously Levenshtein distance and Longest common subsequence don't fulfill this requirement. Using Jaccard distance on the set of n-grams gives good results but has other drawbacks (it's a pseudometric and higher n results in higher penalty for changing single character). [original research] As I thought about it, what I'm looking for is a function f(A,B) such that f(A,B)+1 equals the minimum number of blocks that one have to divide A into (A1 ... An), apply a permutation on the blocks and get B: f("hello", "hello") = 0 f("helloworld", "worldhello") = 1 // hello world -> world hello f("abba", "baba") = 2 // ab b a -> b ab a f("computer", "copmuter") = 3 // co m p uter -> co p m uter This can be extended for A and B that aren't necessarily permutations of each other: any additional character that can't be matched is considered as one additional block. f("computer", "combuter") = 3 // com uter -> com uter, unmatched: p and b. Observing that instead of counting blocks we can count the number of pairs of indices that are taken apart by a permutation, we can write f(A,B) formally as: f(A,B) = min { C(P) | P:|A|?|B|, P is bijective, ?i?dom(P) A[P(i)]=B[P(i)] } C(P) = |A| + |B| - |dom(P)| - |{ i | i,i+1?dom(P) and P(i)+1=P(i+1) }| - 1 The problem is... guess what... ... that I'm not able to calculate this in polynomial time. Can someone suggest a way to do this efficiently? Or perhaps point me to already known metric that exhibits similar properties?

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  • Is there a faster way to parse through a large file with regex quickly?

    - by Ray Eatmon
    Problem: Very very, large file I need to parse line by line to get 3 values from each line. Everything works but it takes a long time to parse through the whole file. Is it possible to do this within seconds? Typical time its taking is between 1 minute and 2 minutes. Example file size is 148,208KB I am using regex to parse through every line: Here is my c# code: private static void ReadTheLines(int max, Responder rp, string inputFile) { List<int> rate = new List<int>(); double counter = 1; try { using (var sr = new StreamReader(inputFile, Encoding.UTF8, true, 1024)) { string line; Console.WriteLine("Reading...."); while ((line = sr.ReadLine()) != null) { if (counter <= max) { counter++; rate = rp.GetRateLine(line); } else if(max == 0) { counter++; rate = rp.GetRateLine(line); } } rp.GetRate(rate); Console.ReadLine(); } } catch (Exception e) { Console.WriteLine("The file could not be read:"); Console.WriteLine(e.Message); } } Here is my regex: public List<int> GetRateLine(string justALine) { const string reg = @"^\d{1,}.+\[(.*)\s[\-]\d{1,}].+GET.*HTTP.*\d{3}[\s](\d{1,})[\s](\d{1,})$"; Match match = Regex.Match(justALine, reg, RegexOptions.IgnoreCase); // Here we check the Match instance. if (match.Success) { // Finally, we get the Group value and display it. string theRate = match.Groups[3].Value; Ratestorage.Add(Convert.ToInt32(theRate)); } else { Ratestorage.Add(0); } return Ratestorage; } Here is an example line to parse, usually around 200,000 lines: 10.10.10.10 - - [27/Nov/2002:16:46:20 -0500] "GET /solr/ HTTP/1.1" 200 4926 789

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  • compare function for upper_bound / lower_bound

    - by Martin Beckett
    I want to find the first item in a sorted vector that has a field less than some value x. I need to supply a compare function that compares 'x' with the internal value in MyClass but I can't work out the function declaration. Can't I simply overload '<' but how do I do this when the args are '&MyClass' and 'float' ? float x; std::vector< MyClass >::iterator last = std::upper_bound(myClass.begin(),myClass.end(),x);

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  • Grouping php array items based on user and created time

    - by Jim
    This is an array of objects showing a user uploading photos: Array ( [12] => stdClass Object ( [type] => photo [created] => 2010-05-14 23:36:41 [user] => stdClass Object ( [id] => 760 [username] => mrsmith ) [photo] => stdClass Object ( [id] => 4181 ) ) [44] => stdClass Object ( [type] => photo [created] => 2010-05-14 23:37:15 [user] => stdClass Object ( [id] => 760 [username] => mrsmith ) [photo] => stdClass Object ( [id] => 4180 ) ) ) However instead of showing: mr smith uploaded one photo mr smith uploaded one photo I'd like to display: mr smith uploaded two photos by grouping similar items, grouping by user ID and them having added them within, let's say 15 minutes of each other. So I'd like to get the array in this sort of shape: Array ( [12] => stdClass Object ( [type] => photo [created] => 2010-05-14 23:36:41 [user] => stdClass Object ( [id] => 760 [username] => mrsmith ) [photos] => Array ( [0] => stdClass Object ( [id] => 4181 ) [1] => stdClass Object ( [id] => 4180 ) ) ) ) preserving the first item of the group and it's created time, and supplementing it with any other groupable photos and then unsetting any items that were grouped (so the final array doesn't have key 44 anymore as it was grouped in with 12). The array contains other actions than just photos, hence the original keys of 12 and 44. I just can't figure out a way to do this efficiently. I used to use MySQL and PHP to do this but am trying to just use pure PHP for caching reasons. Can anyone shed any insights? I thought about going through each item and seeing if I can group it with the previous one in the array but the previous one might not necessarily be relevant or even a photo. I've got total brain freeze :(

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  • Best data-structure to use for two ended sorted list

    - by fmark
    I need a collection data-structure that can do the following: Be sorted Allow me to quickly pop values off the front and back of the list Remain sorted after I insert a new value Allow a user-specified comparison function, as I will be storing tuples and want to sort on a particular value Thread-safety is not required Optionally allow efficient haskey() lookups (I'm happy to maintain a separate hash-table for this though) My thoughts at this stage are that I need a priority queue and a hash table, although I don't know if I can quickly pop values off both ends of a priority queue. I'm interested in performance for a moderate number of items (I would estimate less than 200,000). Another possibility is simply maintaining an OrderedDictionary and doing an insertion sort it every-time I add more data to it. Furthermore, are there any particular implementations in Python. I would really like to avoid writing this code myself.

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  • nth smallest number among two databases of size n each using divide and conquer

    - by urfriend
    we have two databases of size n containing numbers without repeats. So, in total we have 2n elements. They can be accessed through a query to one database at a time. The query is such that you give it a k and it returns kth smallest entry in that database. we need to find nth smallest entry among all the 2n elements in O(logn) queries. the idea is to use divide and conquer but i need some help thinking through this. thanks!

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  • find word and score based on positions

    - by ryder1211212
    hey guys i have a textfile i have divided it into 4 parts. i want to search each part for the words that appear in each part and score that word exmaple welcome to the national basketball finals,the basketball teams here today have come a long way. without much delay lets play basketball. i will want to return national = 1 as it appears only in one part etc am working on determining text context using word position. am working with c# and not very good in text processing basically if a word appears in the 4 sections it scores 4 if a word appears in the 3 sections it scores 3 if a word appears in the 2 sections it scores 2 if a word appears in the 1 section it scores 1 thanks in advance so far i have this var s = "welcome to the national basketball finals,the basketball teams here today have come a long way. without much delay lets play basketball. "; var numberOfParts = 4; var eachPartLength = s.Length / numberOfParts; var parts = new List<string>(); var words = Regex.Split(s, @"\W").Where(w => w.Length > 0); // this splits all words, removes empty strings var wordsIndex = 0; for (int i = 0; i < numberOfParts; i++) { var sb = new StringBuilder(); while (sb.Length < eachPartLength && wordsIndex < words.Count()) { sb.AppendFormat("{0} ", words.ElementAt(wordsIndex)); wordsIndex++; } // here you have the part Response.Write("[{0}]"+ sb); parts.Add(sb.ToString()); var allwords = parts.SelectMany(p => p.Split(' ').Distinct()); var wordsInAllParts = allwords.Where(w => parts.All(p => p.Contains(w))).Distinct();

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  • How do we achieve "substring-match" under O(n) time?

    - by Pacerier
    I have an assignment that requires reading a huge file of random inputs, for example: Adana Izmir Adnan Menderes Apt Addis Ababa Aden ADIYAMAN ALDAN Amman Marka Intl Airport Adak Island Adelaide Airport ANURADHAPURA Kodiak Apt DALLAS/ADDISON Ardabil ANDREWS AFB etc.. If I specify a search term, the program is supposed to find the lines whereby a substring occurs. For example, if the search term is "uradha", the program is supposed to show ANURADHAPURA. If the search term is "airport", the program is supposed to show Amman Marka Intl Airport, Adelaide Airport A quote from the assignment specs: "You are to program this application taking efficiency into account as though large amounts of data and processing is involved.." I could easily achieve this functionality using a loop but the performance would be O(n). I was thinking of using a trie but it seems to only work if the substring starts from index 0. I was wondering what solutions are there which gives a performance better than O(n)?

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  • question about polynomial multiplication

    - by davit-datuashvili
    i know that horners method for polynomial pultiplication is faster but here i dont know what is happening here is code public class horner{ public static final int n=10; public static final int x=7; public static void main(String[] args){ //non fast version int a[]=new int[]{1,2,3,4,5,6,7,8,9,10}; int xi=1; int y=a[0]; for (int i=1;i<n;i++){ xi=x*xi; y=y+a[i]*xi; } System.out.println(y); //fast method int y1=a[n-1]; for (int i=n-2;i>=0;i--){ y1=x*y+a[i]; } System.out.println(y1); } } result of this two methods are not same result of first method is 462945547 and result of second method is -1054348465 please help

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  • Why is my producer-consumer blocking?

    - by User007
    My code is here: http://pastebin.com/Fi3h0E0P Here is the output 0 Should we take order today (y or n): y Enter order number: 100 More customers (y or n): n Stop serving customers right now. Passing orders to cooker: There are total of 1 order(s) 1 Roger, waiter. I am processing order #100 The goal is waiter must take orders and then give them to the cook. The waiter has to wait cook finishes all pizza, deliver the pizza, and then take new orders. I asked how P-V work in my previous post here. I don't think it has anything to do with \n consuming? I tried all kinds of combination of wait(), but none work. Where did I make a mistake? The main part is here: //Producer process if(pid > 0) { while(1) { printf("0"); P(emptyShelf); // waiter as P finds no items on shelf; P(mutex); // has permission to use the shelf waiter_as_producer(); V(mutex); // cooker now can use the shelf V(orderOnShelf); // cooker now can pickup orders wait(); printf("2"); P(pizzaOnShelf); P(mutex); waiter_as_consumer(); V(mutex); V(emptyShelf); printf("3 "); } } if(pid == 0) { while(1) { printf("1"); P(orderOnShelf); // make sure there is an order on shelf P(mutex); //permission to work cooker_as_consumer(); // take order and put pizza on shelf printf("return from cooker"); V(mutex); //release permission printf("just released perm"); V(pizzaOnShelf); // pizza is now on shelf printf("after"); wait(); printf("4"); } } So I imagine this is the execution path: enter waiter_as_producer, then go to child process (cooker), then transfer the control back to parent, finish waiter_as_consumer, switch back to child. The two waits switch back to parent (like I said I tried all possible wait() combination...).

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  • How do I detect a loop in this linked list?

    - by jjujuma
    Say you have a linked list structure in Java. It's made up of Nodes: class Node { Node next; // some user data } and each Node points to the next node, except for the last Node, which has null for next. Say there is a possibility that the list can contain a loop - i.e. the final Node, instead of having a null, has a reference to one of the nodes in the list which came before it. What's the best way of writing boolean hasLoop(Node first) which would return true if the given Node is the first of a list with a loop, and false otherwise? How could you write so that it takes a finite amount of space and a reasonable amount of time?

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  • Could a truly random number be generated using pings to psuedo-randomly selected IP addresses?

    - by _ande_turner_
    The question posed came about during a 2nd Year Comp Science lecture while discussing the impossibility of generating numbers in a deterministic computational device. This was the only suggestion which didn't depend on non-commodity-class hardware. Subsequently nobody would put their reputation on the line to argue definitively for or against it. Anyone care to make a stand for or against. If so, how about a mention as to a possible implementation?

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  • Python - How to find a correlation between two vectors ?

    - by psihodelia
    Given two vectors X and Y I have to find their correlation, i.e. their linear dependence/independence. Both vectors have equal dimension. A resulted answer should be a floating point number from [-1.0 .. 1.0]. Example: X=[-1, 2, 0] Y=[ 4, 2, -0.3] Find y=cor(X,Y) such that y belongs to [-1.0 .. 1.0]. It should be a simple construction involving a list-comprehension. No external library is allowed. UPDATE: ok, if dot product is enough, then here is my solution: nX = 1/(sum([x*x for x in X]) ** 0.5) nY = 1/(sum([y*y for y in Y]) ** 0.5) cor = sum([(x*nX)*(y*nY) for x,y in zip(X,Y) ]) right?

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  • make tree in scheme

    - by ???
    (define (entry tree) (car tree)) (define (left-branch tree) (cadr tree)) (define (right-branch tree) (caddr tree)) (define (make-tree entry left right) (list entry left right)) (define (mktree order items_list) (cond ((= (length items_list) 1) (make-tree (car items_list) '() '())) (else (insert2 order (car items_list) (mktree order (cdr items_list)))))) (define (insert2 order x t) (cond ((null? t) (make-tree x '() '())) ((order x (entry t)) (make-tree (entry t) (insert2 order x (left-branch t)) (right-branch t))) ((order (entry t) x ) (make-tree (entry t) (left-branch t) (insert2 order x (right-branch t)))) (else t))) The result is: (mktree (lambda (x y) (< x y)) (list 7 3 5 1 9 11)) (11 (9 (1 () (5 (3 () ()) (7 () ()))) ()) ()) But I'm trying to get: (7 (3 (1 () ()) (5 () ())) (9 () (11 () ()))) Where is the problem?

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  • Graph - strongly connected components

    - by HardCoder1986
    Hello! Is there any fast way to determine the size of the largest strongly connected component in a graph? I mean, like, the obvious approach would mean determining every SCC (could be done using two DFS calls, I suppose) and then looping through them and taking the maximum. I'm pretty sure there has to be some better approach if I only need to have the size of that component and only the largest one, but I can't think of a good solution. Any ideas? Thanks.

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