std

问题 Is there a one liner (or a simple loop-free) solution to sort a vector by its even and odd indices? Example: long entries[] = {0,1,2,10,11}; // indices 0 1 2 3 4 std::vector<long> vExample(entries, entries + sizeof(entries) / sizeof(long) ); vExample.sortEvenOdd(vExample.begin(),vExample.end()); // magic one liner I wish existed... for (int i = 0; i < vExample.size(); i++) { std::cout << vExample[i] << " "; } Now I'd like to have the following output: 0 2 11 1 10 // corresponding to indices 0

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: C++ char* vs std::string I'm new to C++ coming from C# but I really do like C++ much better. I have an abstract class that defines two constant strings (not static). And I wondered if a const char* would be a better choice. I'm still getting the hang of the C++ standards, but I just figured that there really isn't any reason why I would need to use std::string in this particular case (no appending or editing the

问题 How is it possible to use parts of the C++ STL in Enterprise Architect? It would be nice to be able to specify certain class attributes as std::string or use std::auto_ptr (or even std::tr1::shared_ptr ) as types. Another interesting thing would be how one is able to integrate container-types like std::vector and std::map into EA. 回答1: I have taught how STL containers look like to EA, I guess it can be extended to stl pointers too: Forward engineering: You can define collection classes for

问题 I am trying to choose between map and unordered_map for the following use case: The key of the map is a pointer. The most common use case is that there will be a single element in the map. In general, the max number of elements in the map less than 10. The map is accessed very often and speed is the most important factor. Changes to the map are infrequent. While measuring the speed is obviously the correct approach here, this code will be used on several platforms so I'm trying to create a

问题 Is it possible to use the std::array<class T, std::size_t N> as a private attribute of a class but initialize its size in the constructor of the class? class Router{ std::array<Port,???> ports; //I dont know how much ports do will this have public: Switch(int numberOfPortsOnRouter){ ports=std::array<Port,numberOfPortsOnRouter> ports; //now I know it has "numberOfPortsOnRouter" ports, but howto tell the "ports" variable? } } I might use a pointer, but could this be done without it? 回答1: No,

问题 I want to fill some structure while finding minimum element. Pl find the code below tyoedef struct Point { double x, y; }Point; I have a vector of points - std::vector<Point> V in which i have few thousand points. There is another struct I have typedef struct cart { Point pt; double val_1; // computed using only Pt double val_2; // computer using only Pt }cart; Now I have two tasks: I need to find minimum element from structure V. Fill the structure cart, which is directly dependent on V. I

问题 This question already has answers here : Am I missing anything here in my statement about c++? (5 answers) Closed 4 years ago . #include <map> #include <string> std::map<std::string, int> foo; foo["bar"] = 1; Why do I get the error "expression must be an integral constant expression" in visual studio 12? I can't work this one out... 回答1: You need to place the code inside a function. #include <map> #include <string> void xyz() { std::map<std::string, int> foo; foo["bar"] = 1; } I verified VS

问题 Is there any stdlib-like library for bare-metal programming? I am trying to build a program (supposed to be built on linux) for bare-metal environment. The program is dependent on stdlib and posix lib (malloc, calloc, realloc, free, and pthread usage). I will modify it for single thread anyway. I was reading https://www.ibm.com/developerworks/aix/tutorials/au-memorymanager/ and maybe I will implement my own memory management. But in my case the program has malloc/realloc/free s of various

问题 For a task, I'm doing some simple data sampling to determine which samples contains audio counting the total number of energy. I've been looking into the std::count_if function, and, although this suits my needs to a certain extent, for example: int foo = std::count_if( std::begin(samples), std::end(samples), containsSound); This counts the total number of samples that contain sound, but does not give an indication to the samples that contain sound. I came up with this solution: std::vector

问题 I have image stream from my AVCaptureVideoDataOutputSampleBufferDelegate method: - (void)captureOutput:(AVCaptureOutput )captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection )connection; 
Then I want to take sampleBuffer and provide it for C++ openalrp library to recognize which takes image bytes or raw pixel data. What function should I use and how to convert sampleBuffer to suitable input type, std::vector<char> or unsigned char* pixelData