stl

问题 I want to iterate through a STL set to do operations on elements pairwise in the set. For eg. if set S={1,2,3), I need to be able to check {1,2},{2,3},{1,3}. So a very wrong C++ code for this would be as follows- set<bitset<2501> > arr; unsigned sz = arr.size(); rep(i,sz-1) { for(j=i+1;j<sz;j++) { //do processing and in my case is an OR operation if(((arr[i])|(arr[j])) == num) { cnt++; } } } I wrote the above wrong code to give you a better idea of what I want to do. A better version (should

问题 i'm trying to ready a binary-file into a set of variables using the c++ std::ifstream class. The following example works: std::ifstream inFile; inFile.open("example.bin"); uint8_t temp8; uint16_t temp16; inFile >> temp8; inFile >> temp8; But if i replace the last two lines with one line inFile >> temp16; nothing is read and inFile.fail() returns true . Can anyone explain, why I can't read into a 16 bit variable? 回答1: The operator>> overload for reading uint16_t from istreams is a formatted

问题 I have a dll ( my_library.dll ) that exports a struct using __ declspec(dllexport) . Since this struct contains an std::vector<std::wstring> member , I've also exported functions for it like so: template class __declspec(dllexport) std::allocator<std::wstring>; template class __declspec(dllexport) std::vector<std::wstring>; Please note that I've defined macros such that dll exports above struct and vector when compiling and they are imported (via __declspec(dllimport)) when the dll is being

问题 I found one page link: Convert Three.js to .stl for 3D printing? var exporter = new THREE.STLExporter(); var str = exporter.parse(scene); console.log(str); But when I'm using them, not export a stl file. How can I do then? 回答1: The STLExporter.parse() will export the specified object to a string. If you wish to save the string as a file you have to perform some more operations. As a simple approach you can use FileSaver.js for saving the string to a file. First of all you have to download and

问题 I have this code (roughly) in a cpp app: QList<Foo> rawAssets = getlist(); QVector<std::pair<QString, QString>> assets; std::transform(rawAssets.begin(), rawAssets.end(), assets.begin(), makePair); That causes exc_bad_access to throw when I use assets again. However, if I change assets.begin() to std::back_inserter(assets) then it works as I expect. I found tutorials for std::transform showing both kinds of usage. Why is it wrong in my case? 回答1: Since you've just declared QVector<std::pair

问题 I have a strong use-case to define my own sorting algorithm, which is faster than the fastest in stl and by exploiting some nice properties of the underlying data I basically can sort in O(n) . So far so good, now the problem is that I would like to offer a generic interface which will fit any type of container e.g. T* or std::vector<T> etc, as long as couple of key concepts apply e.g. there is a valid operator [] available to access the elements of the collection the elements of the

问题 I have the following code which seems to work: class MapCell { public: int x, y, z; }; void Test3DVector(int size_x, int size_y, int size_z) { vector< vector< vector<MapCell> > > m(size_x, vector<vector<MapCell>>(size_y, vector<MapCell>(size_z))); for (int x = 0; x < size_x; ++x) { for (int y = 0; y < size_y; ++y) { for (int z = 0; z < size_z; ++z) { m[x][y][z].x = x; m[x][y][z].y = y; m[x][y][z].z = z; } } } } I want to write a class that has the 3D vector as a member variable, with the

问题 I have a sample program in which I am trying to see how the iterator invalidates while deleting the elements from a map. The program is here: #include <iostream> #include <map> using namespace std; int main(int argc, char *argv[]) { map<int, int> myMap; myMap.insert(pair<int, int>(0, 2)); myMap.insert(pair<int, int>(1, 4)); myMap.insert(pair<int, int>(3, 18)); myMap.insert(pair<int, int>(2, 20)); map<int, int>::iterator it; for(it = myMap.begin(); it != myMap.end(); ++it) { myMap.erase(it); /

问题 In creating a code common for set , unordered_set , map , and unordered_map , I need the few methods, where the handling is actually different. My problem is getting the compiler to deduce, which implementation to use. Consider the example: #include <map> #include <unordered_set> #include <string> #include <iostream> using namespace std; static unordered_set<string> quiet; static map<const string, const string> noisy; template <template <typename ...> class Set, typename K> static void insert

问题 While using gdb for the following code, it appears that pretty print works as expected for stl vector and strings but the output for list seems cryptic. list<int> l; string a = "Hello"; vector<int> v(2,3); l.push_back(5); l.push_back(10); Output of gdb pretty print: (gdb) set print pretty on (gdb) disp v 1: v = std::vector of length 2, capacity 2 = {3, 3} (gdb) disp a 2: a = "Hello" (gdb) disp l 3: l = { <std::__cxx11::_List_base<int, std::allocator<int> >> = { _M_impl = { <std::allocator<std