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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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  • How can I find the closest vector to another in a specific direction?

    - by Sniper
    Perhaps I am not phrasing it incorrectly in my searches, but I can not find anything on this. I have a vector3 with a specific direction that it is facing, I want to get the closest object to that position in that specific direction. Basically I want to get the object that is being aimed at. I have thought about finding all objects within a box and then finding the closest object to my vector from them results, but I am sure that there is a more efficient way. The Z axis is optional, the objects are most likely within a few meters of the search vector. http://i.stack.imgur.com/FafAu.jpg

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  • Vector of Object Pointers, general help and confusion

    - by Staypuft
    Have a homework assignment in which I'm supposed to create a vector of pointers to objects Later on down the load, I'll be using inheritance/polymorphism to extend the class to include fees for two-day delivery, next day air, etc. However, that is not my concern right now. The final goal of the current program is to just print out every object's content in the vector (name & address) and find it's shipping cost (weight*cost). My Trouble is not with the logic, I'm just confused on few points related to objects/pointers/vectors in general. But first my code. I basically cut out everything that does not mater right now, int main, will have user input, but right now I hard-coded two examples. #include <iostream> #include <string> #include <vector> using namespace std; class Package { public: Package(); //default constructor Package(string d_name, string d_add, string d_zip, string d_city, string d_state, double c, double w); double calculateCost(double, double); void Print(); ~Package(); private: string dest_name; string dest_address; string dest_zip; string dest_city; string dest_state; double weight; double cost; }; Package::Package() { cout<<"Constucting Package Object with default values: "<<endl; string dest_name=""; string dest_address=""; string dest_zip=""; string dest_city=""; string dest_state=""; double weight=0; double cost=0; } Package::Package(string d_name, string d_add, string d_zip, string d_city, string d_state, string r_name, string r_add, string r_zip, string r_city, string r_state, double w, double c){ cout<<"Constucting Package Object with user defined values: "<<endl; string dest_name=d_name; string dest_address=d_add; string dest_zip=d_zip; string dest_city=d_city; string dest_state=d_state; double weight=w; double cost=c; } Package::~Package() { cout<<"Deconstructing Package Object!"<<endl; delete Package; } double Package::calculateCost(double x, double y){ return x+y; } int main(){ double cost=0; vector<Package*> shipment; cout<<"Enter Shipping Cost: "<<endl; cin>>cost; shipment.push_back(new Package("tom r","123 thunder road", "90210", "Red Bank", "NJ", cost, 10.5)); shipment.push_back(new Package ("Harry Potter","10 Madison Avenue", "55555", "New York", "NY", cost, 32.3)); return 0; } So my questions are: I'm told I have to use a vector of Object Pointers, not Objects. Why? My assignment calls for it specifically, but I'm also told it won't work otherwise. Where should I be creating this vector? Should it be part of my Package Class? How do I go about adding objects into it then? Do I need a copy constructor? Why? What's the proper way to deconstruct my vector of object pointers? Any help would be appreciated. I've searched for a lot of related articles on here and I realize that my program will have memory leaks. Using one of the specialized ptrs from boost:: will not be available for me to use. Right now, I'm more concerned with getting the foundation of my program built. That way I can actually get down to the functionality I need to create. Thanks.

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  • Reading and writing C++ vector to a file

    - by JB
    For some graphics work I need to read in a large amount of data as quickly as possible and would ideally like to directly read and write the data structures to disk. Basically I have a load of 3d models in various file formats which take too long to load so I want to write them out in their "prepared" format as a cache that will load much faster on subsequent runs of the program. Is it safe to do it like this? My worries are around directly reading into the data of the vector? I've removed error checking, hard coded 4 as the size of the int and so on so that i can give a short working example, I know it's bad code, my question really is if it is safe in c++ to read a whole array of structures directly into a vector like this? I believe it to be so, but c++ has so many traps and undefined behavour when you start going low level and dealing directly with raw memory like this. I realise that number formats and sizes may change across platforms and compilers but this will only even be read and written by the same compiler program to cache data that may be needed on a later run of the same program. #include <fstream> #include <vector> using namespace std; struct Vertex { float x, y, z; }; typedef vector<Vertex> VertexList; int main() { // Create a list for testing VertexList list; Vertex v1 = {1.0f, 2.0f, 3.0f}; list.push_back(v1); Vertex v2 = {2.0f, 100.0f, 3.0f}; list.push_back(v2); Vertex v3 = {3.0f, 200.0f, 3.0f}; list.push_back(v3); Vertex v4 = {4.0f, 300.0f, 3.0f}; list.push_back(v4); // Write out a list to a disk file ofstream os ("data.dat", ios::binary); int size1 = list.size(); os.write((const char*)&size1, 4); os.write((const char*)&list[0], size1 * sizeof(Vertex)); os.close(); // Read it back in VertexList list2; ifstream is("data.dat", ios::binary); int size2; is.read((char*)&size2, 4); list2.resize(size2); // Is it safe to read a whole array of structures directly into the vector? is.read((char*)&list2[0], size2 * sizeof(Vertex)); }

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  • C++ vector and segmentation faults

    - by Headspin
    I am working on a simple mathematical parser. Something that just reads number = 1 + 2; I have a vector containing these tokens. They store a type and string value of the character. I am trying to step through the vector to build an AST of these tokens, and I keep getting segmentation faults, even when I am under the impression my code should prevent this from happening. Here is the bit of code that builds the AST: struct ASTGen { const vector<Token> &Tokens; unsigned int size, pointer; ASTGen(const vector<Token> &t) : Tokens(t), pointer(0) { size = Tokens.size() - 1; } unsigned int next() { return pointer + 1; } Node* Statement() { if(next() <= size) { switch(Tokens[next()].type) { case EQUALS : Node* n = Assignment_Expr(); return n; } } advance(); } void advance() { if(next() <= size) ++pointer; } Node* Assignment_Expr() { Node* lnode = new Node(Tokens[pointer], NULL, NULL); advance(); Node* n = new Node(Tokens[pointer], lnode, Expression()); return n; } Node* Expression() { if(next() <= size) { advance(); if(Tokens[next()].type == SEMICOLON) { Node* n = new Node(Tokens[pointer], NULL, NULL); return n; } if(Tokens[next()].type == PLUS) { Node* lnode = new Node(Tokens[pointer], NULL, NULL); advance(); Node* n = new Node(Tokens[pointer], lnode, Expression()); return n; } } } }; ... ASTGen AST(Tokens); Node* Tree = AST.Statement(); cout << Tree->Right->Data.svalue << endl; I can access Tree->Data.svalue and get the = Node's token info, so I know that node is getting spawned, and I can also get Tree->Left->Data.svalue and get the variable to the left of the = I have re-written it many times trying out different methods for stepping through the vector, but I always get a segmentation fault when I try to access the = right node (which should be the + node) Any help would be greatly appreciated.

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  • Vector Troubles in C++

    - by DistortedLojik
    I am currently working on a project that deals with a vector of objects of a People class. The program compiles and runs just fine, but when I use the debugger it dies when trying to do anything with the PersonWrangler object. I currently have 3 different classes, one for the person, a personwrangler which handles all of the people collectively, and a game class that handles the game input and output. Edit: My basic question is to understand why it is dying when it calls outputPeople. Also I would like to understand why my program works exactly as it should unless I use the debugger. The outputPeople function works the way I intended that way. Edit 2: The callstack has 3 bad calls which are: std::vector ::begin(this=0xbaadf00d) std::vector ::size(this=0xbaadf00d) PersonWrangler::outputPeople(this=0xbaadf00d) Relevant code: class Game { public: Game(); void gameLoop(); void menu(); void setStatus(bool inputStatus); bool getStatus(); PersonWrangler* hal; private: bool status; }; which calls outputPeople where it promptly dies from a baadf00d error. void Game::menu() { hal->outputPeople(); } where hal is an object of PersonWrangler type class PersonWrangler { public: PersonWrangler(int inputStartingNum); void outputPeople(); vector<Person*> peopleVector; vector<Person*>::iterator personIterator; int totalPeople; }; and the outputPeople function is defined as void PersonWrangler::outputPeople() { int totalConnections = 0; cout << " Total People:" << peopleVector.size() << endl; for (unsigned int i = 0;i < peopleVector.size();i++) { sort(peopleVector[i]->connectionsVector.begin(),peopleVector[i]->connectionsVector.end()); peopleVector[i]->connectionsVector.erase( unique (peopleVector[i]->connectionsVector.begin(),peopleVector[i]->connectionsVector.end()),peopleVector[i]->connectionsVector.end()); peopleVector[i]->outputPerson(); totalConnections+=peopleVector[i]->connectionsVector.size(); } cout << "Total connections:" << totalConnections/2 << endl; }

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  • How Do I Search For Struct Items In A Vector? [migrated]

    - by Vladimir Marenus
    I'm attempting to create an inventory system using a vector implementation, but I seem to be having some troubles. I'm running into issues using a struct I made. NOTE: This isn't actually in a game code, this is a separate Solution I am using to test my knowledge of vectors and structs! struct aItem { string itemName; int damage; }; int main() { aItem healingPotion; healingPotion.itemName = "Healing Potion"; healingPotion.damage= 6; aItem fireballPotion; fireballPotion.itemName = "Potion of Fiery Balls"; fireballPotion.damage = -2; vector<aItem> inventory; inventory.push_back(healingPotion); inventory.push_back(healingPotion); inventory.push_back(healingPotion); inventory.push_back(fireballPotion); if(find(inventory.begin(), inventory.end(), fireballPotion) != inventory.end()) { cout << "Found"; } system("PAUSE"); return 0; } The preceeding code gives me the following error: 1c:\program files (x86)\microsoft visual studio 11.0\vc\include\xutility(3186): error C2678: binary '==' : no operator found which takes a left-hand operand of type 'aItem' (or there is no acceptable conversion) There is more to the error, if you need it please let me know. I bet it's something small and silly, but I've been thumping at it for over two hours. Thanks in advance!

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  • Vector vs Scalar velocity?

    - by Serguei Fedorov
    I am revamping an engine I have been working on and off on for the last few weeks to use a directional vector to dictate direction; this way I can dictate the displacement based on a direction. However, the issue I am trying to overcome is the following problem; the speed towards X and speed towards Y are unrelated to one another. If gravity pulls the object down by an increasing velocity my velocity towards the X should not change. This is very easy to implement if my speed is broken into a Vector datatype, Vector.X dictates one direction Vector.Y dictates the other (assuming we are not concerned about the Z axis). However, this defeats the purpose of the directional vector because: SpeedX = 10 SpeedY = 15 [1, 1] normalized = ~[0.7, 0.7] [0.7, 0.7] * [10, 15] = [7, 10.5] As you can see my direction is now "scaled" to my speed which is no longer the direction that I want to be moving in. I am very new to vector math and this is a learning project for me. I looked around a little bit on the internet but I still want to figure out things on my own (not just look at an example and copy off it). Is there way around this? Using a directional vector is extremely useful but I am a little bit stumped at this problem. I am sorry if my mathematical understanding maybe completely wrong.

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  • Calculating up-vector to avoid gimbal lock using euler angles

    - by jessejuicer
    I wish to orbit a camera around a sphere, yet the problem is that when the camera rotates so that it is at the north pole (and pointing down) or the south pole (and pointing up) of the sphere the camera doesn't handle itself very well. It spins rapidly until arriving 180 degrees in the opposite direction. I believe this is known as gimbal lock. I understand you can avoid this problem using quaternions. But I also read in another forum that it's possible to avoid this easily using euler angles as well. Which I would prefer to do. It was said that all you need to do is "calculate a proper up-vector every frame, and that avoids the problem entirely." Well, I tried aligning the up-vector with the vertical axis of the camera whenever the camera changed orientation, but this didn't seem to work. Meaning that the up-vector followed exactly the orientation of the camera's y-axis (or it's up vector), instead of using a constant up-vector aligned to the up-vector of the world (0, 1, 0). How exactly do I go about calculating a proper up-vector as my camera orientation changes to avoid the gimbal lock problem mentioned above?

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  • Double Free inside of a destructor upon adding to a vector

    - by Shawn B
    Hey, I am working on a drum machine, and am having problems with vectors. Each Sequence has a list of samples, and the samples are ordered in a vector. However, when a sample is push_back on the vector, the sample's destructor is called, and results in a double free error. Here is the Sample creation code: class XSample { public: Uint8 Repeat; Uint8 PlayCount; Uint16 Beats; Uint16 *Beat; Uint16 BeatsPerMinute; XSample(Uint16 NewBeats,Uint16 NewBPM,Uint8 NewRepeat); ~XSample(); void GenerateSample(); void PlaySample(); }; XSample::XSample(Uint16 NewBeats,Uint16 NewBPM,Uint8 NewRepeat) { Beats = NewBeats; BeatsPerMinute = NewBPM; Repeat = NewRepeat-1; PlayCount = 0; printf("XSample Construction\n"); Beat = new Uint16[Beats]; } XSample::~XSample() { printf("XSample Destruction\n"); delete [] Beat; } And the 'Dynamo' code that creates each sample in the vector: class XDynamo { public: std::vector<XSample> Samples; void CreateSample(Uint16 NewBeats,Uint16 NewBPM,Uint8 NewRepeat); }; void XDynamo::CreateSample(Uint16 NewBeats,Uint16 NewBPM,Uint8 NewRepeat) { Samples.push_back(XSample(NewBeats,NewBPM,NewRepeat)); } Here is main(): int main() { XDynamo Dynamo; Dynamo.CreateSample(4,120,2); Dynamo.CreateSample(8,240,1); return 0; } And this is what happens when the program is run: Starting program: /home/shawn/dynamo2/dynamo [Thread debugging using libthread_db enabled] XSample Construction XSample Destruction XSample Construction XSample Destruction *** glibc detected *** /home/shawn/dynamo2/dynamo: double free or corruption (fasttop): 0x0804d008 *** However, when the delete [] is removed from the destructor, the program runs perfectly. What is causing this? Any help is greatly appreciated.

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  • Vector insert() causes program to crash

    - by wrongusername
    This is the first part of a function I have that's causing my program to crash: vector<Student> sortGPA(vector<Student> student) { vector<Student> sorted; Student test = student[0]; cout << "here\n"; sorted.insert(student.begin(), student[0]); cout << "it failed.\n"; ... It crashes right at the sorted part because I can see "here" on the screen but not "it failed." The following error message comes up: Debug Assertion Failed! (a long path here...) Expression: vector emplace iterator outside range For more information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts. I'm not sure what's causing the problem now, since I have a similar line of code elsewhere student.insert(student.begin() + position(temp, student), temp); that does not crash (where position returns an int and temp is another declaration of a struct Student). What can I do to resolve the problem, and how is the first insert different from the second one?

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  • Get location of element you just pushed into vector C++

    - by Satchmo Brown
    I am curious about how pushing back into a vector works. I want a way to push back an element and then be able to add it's location in the vector to a double array serving as a type of map. Something like this: // Create a bomb Bomb b; b.currentTime = SDL_GetTicks(); b.explodeTime = SDL_GetTicks() + 3000; b.owner = player; b.power = 2; b.x = x; b.y = y; bombVec.push_back(b); bombs[y][x] = THIS_IS_WHAT_I_WANT; This way when I explode the bomb, I can check the map and then have an ID in the vector to deal with. Every non bomb square will have a -1. Also, just curious. Imagine I have 3 elements in a vector. I delete the second one and then add another. Does the new element go in the same location as the one that was deleted? Thanks!

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  • Loading data from file to Vector structure

    - by owca
    I'm trying to parse through fixed-width formatted file extracting x,y values of points from it, and then storing them in int[] array inside a Vector. Text file looks as follows : 0006 0015 0125 0047 0250 0131 That's the code : Vector<int[]> vc = new Vector<int[]>(); try { BufferedReader file = new BufferedReader(new FileReader("myfile.txt")); String s; int[] vec = new int[2]; while ((s = file.readLine()) != null) { vec[0] = Integer.parseInt(s.substring(0, 4).trim()); vec[1] = Integer.parseInt(s.substring(5, 8).trim()); vc.add(vec); } file.close(); } catch (IOException e) { } for(int i=0; i<vc.size(); i++){ for(int j=0; j<2; j++){ System.out.println(vc.elementAt(i)[j]); } } But the output shows only last line. 250 131 250 131 250 131 Should I somehow use Vector.nextElement() here to get all my data ?

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  • C++ std::vector memory/allocation

    - by aaa
    from a previous question about vector capacity, http://stackoverflow.com/questions/2663170/stdvector-capacity-after-copying, Mr. Bailey said: In current C++ you are guaranteed that no reallocation occurs after a call to reserve until an insertion would take the size beyond the value of the previous call to reserve. Before a call to reserve, or after a call to reserve when the size is between the value of the previous call to reserve and the capacity the implementation is allowed to reallocate early if it so chooses. So, if I understand correctly, in order to assure that no relocation happens until capacity is exceeded, I must do reserve twice? can you please clarify it? I am using vector as a memory stack like this: std::vector<double> memory; memory.reserve(size); memory.insert(memory.end(), matrix.data().begin(), matrix.data().end()); // smaller than size size_t offset = memory.size(); memory.resize(memory.capacity(), 0); I need to guarantee that relocation does not happen in the above. thank you. ps: I would also like to know if there is a better way to manage memory stack in similar manner other than vector

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  • android saveinstance saving vector datatypes

    - by Javadid
    hi friends, I am making an application which is currently working perfectly but with only 1 problem... As we all know that the activity is destroyed and recreated when user changes the orientation of the phone... my activity needs to save a vector full of objects wen the activity is recreated... i checked the OnSaveInstance() method and found that there is no way a vector can be stored... Does any1 have a suggestion for storing vector so that i can retrieve it on recreation of Activity??? Any help will be appreciated... Thanx...

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  • Boost::Container::Vector with Enum Template Argument - Not Legal Base Class

    - by CuppM
    Hi, I'm using Visual Studio 2008 with the Boost v1.42.0 library. If I use an enum as the template argument, I get a compile error when adding a value using push_back(). The compiler error is: 'T': is not a legal base class and the location of the error is move.hpp line 79. #include <boost/interprocess/containers/vector.hpp> class Test { public: enum Types { Unknown = 0, First = 1, Second = 2, Third = 3 }; typedef boost::container::vector<Types> TypesVector; }; int main() { Test::TypesVector o; o.push_back(Test::First); return 0; } If I use a std::vector instead it works. And if I resize the Boost version first and then set the values using the [] operator it also works. Is there some way to make this work using push_back()?

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  • Sorting a vector of (double precision) reals and obtain their order

    - by Philipp
    Hello everyone, in C++ would like to sort a lengthy (2^20) vector of reals, obviously sort() does the trick. Having used R before I was used to the nice order() function which yields the permutation that leads to the sorted vector. Probably someone has done this in C++, maybe it's just my weak google-Fu that prevents me from finding it. And yeah, obivously my C++ newbness could stop me from spotting something straightforward. Example: x = {24, 55, 22, 1} then the permutation perm = {3, 2, 0, 1} maps the original x to the sorted x in ascending order. I can probably implement some bubble sort which does not only sort x but performs the same transpositions on the vector {0,1,2,...} and outputs both, but I believe someone must have thought about it and especially have done it efficiently. Thank you very much, Philipp

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  • Method for exporting drawn flash/flex UIComponent to vector based print file

    - by eshowcase
    Hi, I am creating a flex application where I am using the built in graphics package of flex 3 to draw shapes and things to a UIComponent. I want to be able to export this vector image UIComponent to a vector based file, pdf, eps etc. Are there any tools, libraries, or methods for doing so? I looked at AlivePDF - which works very slick, but its output is effectively a snapshot of the UIComponent drawn out as a bitmap to the PDF. I want true vector output, as this image is for print, needs to be able to scale and be color correct. I read somewhere that it may be possible with Adobe Live Cycle, but in looking at the documentation I'm not sure how to use it. Another possibility is to submit the final image parameters to a server-side PHP script that would re-generate the image in SVG format. But as I understand SVG is not ideal for print, and this is lots of extra work. Any thoughts, ideas, methods? Thanks!

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  • vector segmentation fault

    - by user1849298
    I have a problem with the segmentation fault. Look: #include<fstream> using namespace std; int main(){ int n,i,vector[10001],vectorcopy[10001]; ifstream in("program.in"); ofstream out("program.out"); in>>n; for(i=1;i<=n;i++){ in>>vector[i]; vectorcopy[i]=vector[i]; } return 0;} And the debugger says: Program recived signal SIGSEGV, Segmentation fault Please, tell me what to do!

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  • Counting Values in R Vector

    - by GTyler
    I have a large vector of percentages (0-100) and I am trying to count how many of them are in specific 20% buckets (<20, 20-40, 40-60,60-80,80-100). The vector has length 129605 and there are no NA values. Here's my code: x<-c(0,0,0,0,0) for(i in 1: length(mail_return)) { if (mail_return[i]<=20) { x[1] = x[1] + 1 } if (mail_return[i]>20 && mail_return[i]<=40) { x[2] = x[2] + 1 } if (mail_return[i]>40 && mail_return[i]<=60) { x[3] = x[3] + 1 } if (mail_return[i]>60 && mail_return[i]<=80) { x[4] = x[4] + 1 } else { x[5] = x[5] + 1 } } But sum(x) is giving me length 133171. Shouldn't it be the length of the vector, 129605? What's wrong?

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  • c++ Sorting a vector based on values of other vector, or what's faster?

    - by pollux
    Hi, There are a couple of other posts about sorting a vector A based on values in another vector B. Most of the other answers tell to create a struct or a class to combine the values into one object and use std::sort. Though I'm curious about the performance of such solutions as I need to optimize code which implements bubble sort to sort these two vectors. I'm thinking to use a vector<pair<int,int>> and sort that. I'm working on a blob-tracking application (image analysis) where I try to match previously tracked blobs against newly detected blobs in video frames where I check each of the frames against a couple of previously tracked frames and of course the blobs I found in previous frames. I'm doing this at 60 times per second (speed of my webcam). Any advice on optimizing this is appreciated. The code I'm trying to optimize can be shown here: http://code.google.com/p/projectknave/source/browse/trunk/knaveAddons/ofxBlobTracker/ofCvBlobTracker.cpp?spec=svn313&r=313 Thanks

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  • Java: How to store Vector<String[]> in XML (or save in any other way)

    - by hatboysam
    Basically I have a proof-of-concept application that is a digital recipe book. Each Recipe is an object and each object has, among other fields, a Vector containing arrays. The Vector is the list of all ingredients in the Recipe while each ingredient has an array showing the name of the ingredient, the amount, and the unit for that amount. I want to save each Recipe to XML so that they can be accessed by the user. How can I store a Vector of String arrays in XML or any other sort of file so that it can later be recalled and accessed?

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  • C++ Vector of vectors

    - by xbonez
    I have a class header file called Grid.h that contains the following 2 private data object: vector<int> column; vector<vector<int>> row; And a public method whose prototype in Grid.h is such: int getElement (unsigned int& col, unsigned int& row); The definition of above mentioned function is defined as such in Grid.cpp: int getElement (unsigned int& col, unsigned int& row) { return row[row][col] ; } When I run the program, I get this error: error C2109: subscript requires array or pointer type Whats going wrong?

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  • C++ vector that *doesn't* initialize its members?

    - by Mehrdad
    I'm making a C++ wrapper for a piece of C code that returns a large array, and so I've tried to return the data in a vector<unsigned char>. Now the problem is, the data is on the order of megabytes, and vector unnecessarily initializes its storage, which essentially turns out to cut down my speed by half. How do I prevent this? Or, if it's not possible -- is there some other STL container that would avoid such needless work? Or must I end up making my own container? (Pre-C++11) Note: I'm passing the vector as my output buffer. I'm not copying the data from elsewhere.

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  • Perturb vector by some angle

    - by Myx
    Hello: I have a unit vector in 3D space whose direction I wish to perturb by some angle within the range 0 to theta, with the position of the vector remaining the same. What is a way I can accomplish this? Thanks.

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