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  • What is an efficient algorithm for randomly assigning a pool of objects to a parent using specific rules

    - by maple_shaft
    I need some expert answers to help me determine the most efficient algorithm in this scenario. Consider the following data structures: type B { A parent; } type A { set<B> children; integer minimumChildrenAllowed; integer maximumChildrenAllowed; } I have a situation where I need to fetch all the orphan children (there could be hundreds of thousands of these) and assign them RANDOMLY to A type parents based on the following rules. At the end of the job, there should be no orphans left At the end of the job, no object A should have less children than its predesignated minimum. At the end of the job, no object A should have more children than its predesignated maximum. If we run out of A objects then we should create a new A with default values for minimum and maximum and assign remaining orphans to these objects. The distribution of children should be as evenly distributed as possible. There may already be some children assigned to A before the job starts. I was toying with how to do this but I am afraid that I would just end up looping across the parents sorted from smallest to largest, and then grab an orphan for each parent. I was wondering if there is a more efficient way to handle this?

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  • Efficient way to find unique elements in a vector compared against multiple vectors

    - by SyncMaster
    I am trying find the number of unique elements in a vector compared against multiple vectors using C++. Suppose I have, v1: 5, 8, 13, 16, 20 v2: 2, 4, 6, 8 v3: 20 v4: 1, 2, 3, 4, 5, 6, 7 v5: 1, 3, 5, 7, 11, 13, 15 The number of unique elements in v1 is 1 (i.e. number 16). I tried two approaches. Added vectors v2,v3,v4 and v5 into a vector of vector. For each element in v1, checked if the element is present in any of the other vectors. Combined all the vectors v2,v3,v4 and v5 using merge sort into a single vector and compared it against v1 to find the unique elements. Note: sample_vector = v1 and all_vectors_merged contains v2,v3,v4,v5 //Method 1 unsigned int compute_unique_elements_1(vector<unsigned int> sample_vector,vector<vector<unsigned int> > all_vectors_merged) { unsigned int duplicate = 0; for (unsigned int i = 0; i < sample_vector.size(); i++) { for (unsigned int j = 0; j < all_vectors_merged.size(); j++) { if (std::find(all_vectors_merged.at(j).begin(), all_vectors_merged.at(j).end(), sample_vector.at(i)) != all_vectors_merged.at(j).end()) { duplicate++; } } } return sample_vector.size()-duplicate; } // Method 2 unsigned int compute_unique_elements_2(vector<unsigned int> sample_vector, vector<unsigned int> all_vectors_merged) { unsigned int unique = 0; unsigned int i = 0, j = 0; while (i < sample_vector.size() && j < all_vectors_merged.size()) { if (sample_vector.at(i) > all_vectors_merged.at(j)) { j++; } else if (sample_vector.at(i) < all_vectors_merged.at(j)) { i++; unique ++; } else { i++; j++; } } if (i < sample_vector.size()) { unique += sample_vector.size() - i; } return unique; } Of these two techniques, I see that Method 2 gives faster results. 1) Method 1: Is there a more efficient way to find the elements than running std::find on all the vectors for all the elements in v1. 2) Method 2: Extra overhead in comparing vectors v2,v3,v4,v5 and sorting them. How can I do this in a better way?

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  • What's a good algorithm for a random, uneven distribution of a fixed amount of a resource?

    - by NickC
    Problem I have X, a positive integer, of some resource, R. There are N potential targets. I want to distribute all of R to the N targets in some "interesting" way. "Interesting" means: Some targets may not get any R. It should rarely be near even (with a majority of target getting near X/N of the resource). There should be at least a small chance of one target getting all of R. Bad solutions The naive approach would be to pick a random target and give one R to it and repeat X times. This would result in too even of an approach. The next idea is to pick a random number between 1 and X and give it to a random target. This results in too large of a number (at least X/2 on average) being given to one target. Question This algorithm will be used frequently and I want the distribution to be interesting and uneven so that the surprise doesn't wear off for users. Is there a good algorithm for something in between these two approaches, that fits the definition of interesting above?

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  • What is a good algorithm to distribute items with specific requirements?

    - by user66160
    I have to programmatically distribute a set of items to some entities, but there are rules both on the items and on the entities like so: Item one: 100 units, only entities from Foo Item two: 200 units, no restrictions Item three: 100 units, only entities that have Bar Entity one: Only items that have Baz Entity one hundred: No items that have Fubar I only need to be pointed in the right direction, I'll research and learn the suggested methods.

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  • How to create distinct set from other sets?

    - by shyam_baidya
    While solving the problems on Techgig.com, I got struck with one one of the problem. The problem is like this: A company organizes two trips for their employees in a year. They want to know whether all the employees can be sent on the trip or not. The condition is like, no employee can go on both the trips. Also to determine which employee can go together the constraint is that the employees who have worked together in past won't be in the same group. Examples of the problems: Suppose the work history is given as follows: {(1,2),(2,3),(3,4)}; then it is possible to accommodate all the four employees in two trips (one trip consisting of employees 1& 3 and other having employees 2 & 4). Neither of the two employees in the same trip have worked together in past. Suppose the work history is given as {(1,2),(1,3),(2,3)} then there is no way possible to have two trips satisfying the company rule and accommodating all the employees. Can anyone tell me how to proceed on this problem?

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  • Given an integer, determine if it is a Palindrome in less than O(n) [on hold]

    - by user134235
    There is an O(n) solution to the problem of determining if an integer is a palindrome below. Is it possible to solve this problem in O(log n) or better? static void IsPalindrome(int Number) { int OrignalNum = Number; int Reverse = 0; int Remainder = 0; if (Number > 0) { while (Number > 0) { Remainder = Number % 10; Reverse = Reverse * 10 + Remainder; Number = Number / 10; } if (OrignalNum == Reverse) Console.WriteLine("It is a Palindrome"); else Console.WriteLine("It is not a Palindrome"); } else Console.WriteLine("Enter Number Again"); }

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  • Scale an image with unscalable parts

    - by Uko
    Brief description of problem: imagine having some vector picture(s) and text annotations on the sides outside of the picture(s). Now the task is to scale the whole composition while preserving the aspect ratio in order to fit some view-port. The tricky part is that the text is not scalable only the picture(s). The distance between text and the image is still relative to the whole image, but the text size is always a constant. Example: let's assume that our total composition is two times larger than a view-port. Then we can just scale it by 1/2. But because the text parts are a fixed font size, they will become larger than we expect and won't fit in the view-port. One option I can think of is an iterative process where we repeatedly scale our composition until the delta between it and the view-port satisfies some precision. But this algorithm is quite costly as it involves working with the graphics and the image may be composed of a lot of components which will lead to a lot of matrix computations. What's more, this solution seems to be hard to debug, extend, etc. Are there any other approaches to solving this scaling problem?

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  • Minimizing use of paper

    - by Abody97
    I've recently faced this problem in a dynamic programming curriculum, and I honestly have no idea about how to determine the appropriate state. You're given N (1 <= N <= 70) paragraphs and M (1 <= M <= N) figures. Each paragraph i requires PL_i (1 <= PL_i <= 100) lines and references at most one figure. Each figure is referenced exactly once (i.e., no two paragraphs can reference the same figure, and for each figure there's a paragraph that references it.) Each figure requires PF_i (1 <= PF_i <= 100) lines. The task is to distribute those figures and paragraphs on paper in the order they're given, where one paper fits for L lines at most. No paragraph or figure is too large to fit on one paper. If a paragraph x placed on paper x_p references a figure y then y must be placed on either the paper x_p - 1 or x_p or x_p + 1. We have to find the minimum number of lines (and thus pages) to allocate in order to distribute all the figures and paragraphs. Any help would be extremely appreciated. Thanks in advance!

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  • Fastest way to check if two square 2D arrays are rotationally and reflectively distinct

    - by kustrle
    The best idea I have so far is to rotate first array by {0, 90, 180, 270} degrees and reflect it horizontally or/and vertically. We basically get 16 variations [1] of first array and compare them with second array. if none of them matches the two arrays are rotationally and reflectively distinct. I am wondering if there is more optimal solution than this brute-force approach? [1] 0deg, no reflection 0deg, reflect over x 0deg, reflect over y 0deg, reflect over x and y 90deg, no reflection ...

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  • What can I learn to build a (kind of) recommendation system?

    - by lsmagalhaes
    I'm learning how to develop an android app (nothing serious, just for learning and fun), so I devised the following goal: an app that learns with users actions and, some time later, starts to suggest some useful things. For example: The user add some notes daily, in the morning, and mark some of them as done generally on thursdays and sundays, at evening. Based on that behaviour and the relation of the notes marked as done, the app will prioritize notes that are more propense to be marked, and avoid notifying in days where no note is marked. This is a silly example but I think it ilustrates well what I want to do. I know this is a matter of machine learning, but I don't know where I should start learning. To anyone interested, I'm build a backend in Python, so any libraries or frameworks in this language are very welcome. The frontend, by the way, is sencha touch + phonegap.

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  • Need to organize words based on their components, any other way aside from brute force?

    - by Lathan
    I'm not sure if this process has a name. I have some words (about 9,000). They are in Japanese, but I'll try to explain this using English words. I want to categorize the words by the components (in English, letters). A B C act bar play This should create: A: play B: bar C: act Now, 'a' appears in all 3 words, but I want to make sure that each category (letter) has at least word. Now, it would make sense to delete a word after it's used, but there are a few cases where 2 letters make up one word and that's each letter's only word--so I'd like to account for that somehow. Is there an approach for solving this aside from brute force? Dynamic programming perhaps? Even a name for this process (if it exists) would be great.

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  • Good choice of languages for making a program that manages and organizes business? [closed]

    - by Ronney P
    I've been reading questions and discussions on this website but haven't made an account to start talking or asking anything I had doubts in so please bare with a newbie here. What are specific languages that have are able to make a program that will record, and organize things such as hours, salaries, payments? Also solve business problems, mostly with payments, how much money there will be after interest, taxes and such. Anyway, I've been looking into COBOL, C++, Java, HTML, JavaScript, VB.NET and a couple more. Which ones should I focus on and look into more? I very much appreciate any answers. Thank you.

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  • What is the Big-Oh nitation for this? [closed]

    - by laniam
    procedure quartersearch (x : inter, a1, a2, ?, an) : increasing integers) i := 1{i is left endpoint of search interval} ? j := n {j is right endpoint of search interval} while i < j begin m :=? ?(i + j)? / 4 if x am then ?i := m+1 else if x am then ?m : = ?(i + j)? / 4 else if x am then m := 2 ?(i + j)? /4 else ?if x am then m := 3 ?(i + j)? /4 else j := m end if x = ai then location := i else location := 0

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  • Initialize array in O(1) -- how is this trick called?

    - by user946850
    There is this pattern that trades performance of array access against the need to iterate 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 array has been reset. This has come up in StackOverflow 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.

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  • sum with matlab code

    - by user27089
    i need help it is only put sum in a code line if you can understand in below i have a code in this line below -> X(i,k+1) = X(i,k) + (( X(j,k)-X(i,k))); i want to change it as: X(i,k+1) = X(i,k) + sum(( X(j,k)-X(i,k))); briefly how can I put sum on the code line clear;rand('state', 1); global xLocation; N = 4; xLocation = rand(N,1); t=2;k=1;X=[N,t]; for i=1:N X(i,1)=xLocation(i); end while( k < t ) for i = 1 : N for j = 1 : N X(i,k+1) = X(i,k) + (( X(j,k)-X(i,k))); end end k = k + 1; end

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  • Attempt at Merge Sort: Is this correct? [migrated]

    - by Beatrice
    I am trying to write a merge sort algo. I can't tell if this is actually a canonical merge sort. If I knew how to calculate the runtime I would give that a go. Does anyone have any pointers? Thanks. public static void main(String[] argsv) { int[] A = {2, 4, 5, 7, 1, 2, 3, 6}; int[] L, R; L = new int[A.length/2]; R = new int[A.length/2]; int i = 0, j = 0, k; for (k = 0; k < A.length; k++) { if (k < A.length/2) { L[i] = A[k]; i++; } else { R[j] = A[k]; j++; } } i = 0; j = 0; for (k = 0; k < A.length; k++) { System.out.println(i + " " + j + " " + k); if (i < L.length && j < R.length) { if (L[i] < R[j]) { A[k] = L[i]; i++; } else { A[k] = R[j]; j++; } } } }

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  • How would you solve this graph theory handshake problem in python?

    - by Zachary Burt
    I graduated college last year with a degree in Psychology, but I also took a lot of math for fun. I recently got the book "Introductory Graph Theory" by Gary Chartrand to brush up on my math and have some fun. Here is an exercise from the book that I'm finding particularly befuddling: Suppose you and your husband attended a party with three other married couples. Several handshakes took place. No one shook hands with himself (or herself) or with his (or her) spouse, and no one shook hands with the same person more than once. After all the handshaking was completed, suppose you asked each person, including your husband, how many hands he or she had shaken. Each person gave a different answer. a) How many hands did you shake? b) How many hands did your husband shake? Now, I've been reasoning about this for a while, and trying to draw sample graphs that could illustrate a solution, but I'm coming up empty-handed. My logic is this: there are 8 different vertices in the graph, and 7 of them have different degrees. The values for the degrees must therefore be 0, 1, 2, 3, 4, 5, 6, and x. The # of degrees for one married couple is (0, 6). Since all graphs have an even number of odd vertices, x must be either 5, 3, or 1. What's your solution to this problem? And, if you could solve it in python, how would you do it? (python is fun.) Cheers.

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  • How would you solve this graph theory handshake problem in python?

    - by Zachary Burt
    I graduated college last year with a degree in Psychology, but I also took a lot of math for fun. I recently got the book "Introductory Graph Theory" by Gary Chartrand to brush up on my math and have some fun. Here is an exercise from the book that I'm finding particularly befuddling: Suppose you and your husband attended a party with three other married couples. Several handshakes took place. No one shook hands with himself (or herself) or with his (or her) spouse, and no one shook hands with the same person more than once. After all the handshaking was completed, suppose you asked each person, including your husband, how many hands he or she had shaken. Each person gave a different answer. a) How many hands did you shake? b) How many hands did your husband shake? Now, I've been reasoning about this for a while, and trying to draw sample graphs that could illustrate a solution, but I'm coming up empty-handed. My logic is this: there are 8 different vertices in the graph, and 7 of them have different degrees. The values for the degrees must therefore be 0, 1, 2, 3, 4, 5, 6, and x. The # of degrees for one married couple is (0, 6). Since all graphs have an even number of odd vertices, x must be either 5, 3, or 1. What's your solution to this problem? And, if you could solve it in python, how would you do it? (python is fun.) Cheers.

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  • How can I return an object into PHP userspace from my extension?

    - by John Factorial
    I have a C++ object, Graph, which contains a property named cat of type Category. I'm exposing the Graph object to PHP in an extension I'm writing in C++. As long as the Graph's methods return primitives like boolean or long, I can use the Zend RETURN_*() macros (e.g. RETURN_TRUE(); or RETURN_LONG(123);. But how can I make Graph-getCategory(); return a Category object for the PHP code to manipulate? I'm following the tutorial over at http://devzone.zend.com/article/4486, and here's the Graph code I have so far: #include "php_getgraph.h" zend_object_handlers graph_object_handlers; struct graph_object { zend_object std; Graph *graph; }; zend_class_entry *graph_ce; #define PHP_CLASSNAME "WFGraph" ZEND_BEGIN_ARG_INFO_EX(php_graph_one_arg, 0, 0, 1) ZEND_END_ARG_INFO() ZEND_BEGIN_ARG_INFO_EX(php_graph_two_args, 0, 0, 2) ZEND_END_ARG_INFO() void graph_free_storage(void *object TSRMLS_DC) { graph_object *obj = (graph_object*)object; delete obj-graph; zend_hash_destroy(obj-std.properties); FREE_HASHTABLE(obj-std.properties); efree(obj); } zend_object_value graph_create_handler(zend_class_entry *type TSRMLS_DC) { zval *tmp; zend_object_value retval; graph_object *obj = (graph_object*)emalloc(sizeof(graph_object)); memset(obj, 0, sizeof(graph_object)); obj-std.ce = type; ALLOC_HASHTABLE(obj-std.properties); zend_hash_init(obj-std.properties, 0, NULL, ZVAL_PTR_DTOR, 0); zend_hash_copy(obj-std.properties, &type-default_properties, (copy_ctor_func_t)zval_add_ref, (void*)&tmp, sizeof(zval*)); retval.handle = zend_objects_store_put(obj, NULL, graph_free_storage, NULL TSRMLS_CC); retval.handlers = &graph_object_handlers; return retval; } PHP_METHOD(Graph, __construct) { char *perspectives; int perspectives_len; Graph *graph = NULL; zval *object = getThis(); if(zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &perspectives, &perspectives_len) == FAILURE) { RETURN_NULL(); } graph = new Graph(perspectives); graph_object *obj = (graph_object*)zend_object_store_get_object(object TSRMLS_CC); obj-graph = graph; } PHP_METHOD(Graph, hasCategory) { long perspectiveId; Graph *graph; graph_object *obj = (graph_object*)zend_object_store_get_object(getThis() TSRMLS_CC); graph = obj-graph; if (graph == NULL) { RETURN_NULL(); } if(zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "l", &perspectiveId) == FAILURE) { RETURN_NULL(); } RETURN_BOOL(graph-hasCategory(perspectiveId)); } PHP_METHOD(Graph, getCategory) { // what to do here? RETURN_TRUE; } function_entry php_getgraph_functions[] = { PHP_ME(Graph,__construct,NULL,ZEND_ACC_PUBLIC|ZEND_ACC_CTOR) PHP_ME(Graph,hasCategory,php_graph_one_arg,ZEND_ACC_PUBLIC) PHP_ME(Graph,getCategory,php_graph_one_arg,ZEND_ACC_PUBLIC) { NULL, NULL, NULL } }; PHP_MINIT_FUNCTION(getgraph) { zend_class_entry ce; INIT_CLASS_ENTRY(ce, PHP_CLASSNAME, php_getgraph_functions); graph_ce = zend_register_internal_class(&ce TSRMLS_CC); graph_ce-create_object = graph_create_handler; memcpy(&graph_object_handlers, zend_get_std_object_handlers(), sizeof(zend_object_handlers)); graph_object_handlers.clone_obj = NULL; return SUCCESS; } zend_module_entry getgraph_module_entry = { #if ZEND_MODULE_API_NO = 20010901 STANDARD_MODULE_HEADER, #endif PHP_GETGRAPH_EXTNAME, NULL, /* Functions */ PHP_MINIT(getgraph), NULL, /* MSHUTDOWN */ NULL, /* RINIT */ NULL, /* RSHUTDOWN */ NULL, /* MINFO */ #if ZEND_MODULE_API_NO = 20010901 PHP_GETGRAPH_EXTVER, #endif STANDARD_MODULE_PROPERTIES }; #ifdef COMPILE_DL_GETGRAPH extern "C" { ZEND_GET_MODULE(getgraph) } #endif

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  • pie chart (php graph lib) problem !

    - by gin
    i'm using phpgraphlib for creating charts i tried one of the example of the pie charts ex (with lil bit pf changes) which is : include('phpgraphlib.php'); include('phpgraphlib_pie.php'); $graph = new PHPGraphLibPie(400, 200); $data = array("CBS" = 0, "NBC" = 1); $graph-addData($data); $graph-setTitle('8/29/07 Top 5 TV Networks Market Share'); $graph-setLabelTextColor('50,50,50'); $graph-setLegendTextColor('50,50,50'); $graph-createGraph(); ? and whether i put $data = array("CBS" = 0, "NBC" = 1); or $data = array("CBS" = 1, "NBC" = 0); the pie chart have the same color.. shouldn't the whole pie/slice suppose to be colored with some color (i.e. blue) if ("CBS" = 0, "NBC" = 1) , while if ("CBS" = 1, "NBC" = 0) it should be colored with other color (i.e. red)/? is there any way to fix it? i would really appreciate any help ,,

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  • Neo4j Reading data / performing shortest path calculations on stored data

    - by paddydub
    I'm using the Batch_Insert example to insert Data into the database How can i read this data back from the database. I can't find any examples of how i do this. public static void CreateData() { // create the batch inserter BatchInserter inserter = new BatchInserterImpl( "var/graphdb", BatchInserterImpl.loadProperties( "var/neo4j.props" ) ); Map<String,Object> properties = new HashMap<String,Object>(); properties.put( "name", "Mr. Andersson" ); properties.put( "age", 29 ); long node1 = inserter.createNode( properties ); properties.put( "name", "Trinity" ); properties.remove( "age" ); long node2 = inserter.createNode( properties ); inserter.createRelationship( node1, node2, DynamicRelationshipType.withName( "KNOWS" ), null ); inserter.shutdown(); } I would like to store graph data in the database, graph.makeEdge( "s", "c", "cost", (double) 7 ); graph.makeEdge( "c", "e", "cost", (double) 7 ); graph.makeEdge( "s", "a", "cost", (double) 2 ); graph.makeEdge( "a", "b", "cost", (double) 7 ); graph.makeEdge( "b", "e", "cost", (double) 2 ); Dijkstra<Double> dijkstra = getDijkstra( graph, 0.0, "s", "e" ); What is the best method to store this kind data with 10000's of edges. Then run the Dijskra algorighm to find shortest path calculations using the stored graph data.

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  • Where to find algorithms for standard math functions?

    - by dsimcha
    I'm looking to submit a patch to the D programming language standard library that will allow much of std.math to be evaluated at compile time using the compile-time function evaluation facilities of the language. Compile-time function evaluation has several limitations, the most important ones being: You can't use assembly language. You can't call C code or code for which the source is otherwise unavailable. Several std.math functions violate these and compile-time versions need to be written. Where can I get information on good algorithms for computing things such as logarithms, exponents, powers, and trig functions? I prefer just high level descriptions of algorithms to actual code, for two reasons: To avoid legal ambiguity and the need to make my code look "different enough" from the source to make sure I own the copyright. I want simple, portable algorithms. I don't care about micro-optimization as long as they're at least asymptotically efficient. Edit: D's compile time function evaluation model allows floating point results computed at compile time to differ from those computed at runtime anyhow, so I don't care if my compile-time algorithms don't give exactly the same result as the runtime version as long as they aren't less accurate to a practically significant extent.

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