push-back

问题 I am not sure what to make of this - please tell me what's wrong with the code below. I modified my code to reduce it to the simplest terms. There is a std::vector with a bunch of MyNode objects. The first step is to get a constant reference to one of the data elements of one of these nodes (Data m_data) - in the example below, there is only one node before the 2nd node is inserted as seen below: const cv::Data& currData = m_nodesVector[currIndex].GetData(); MyNode node(...); m_nodesVector

问题 My question is regarding the effect of vector::push_back , I know it adds an element in the end of the vector but what happens underneath the hood? IIRC memory objects are allocated in a sequential manner, so my question is whether vector::push_back simply allocates more memory immediately after the vector, and if so what happens if there is not enough free memory in that location? Or perhaps a pointer is added in the "end" to cause the vector to "hop" to the location it continues? Or is it

问题 I thought that emplace_back would be the winner, when doing something like this: v.push_back(myClass(arg1, arg2)); because emplace_back would construct the object immediately in the vector, while push_back , would first construct an anonymous object and then would copy it to the vector. For more see this question. Google also gives this and this questions. I decided to compare them for a vector that would be filled by integers. Here is the experiment code: #include <iostream> #include <vector

问题 I need to add objects of the same class to a vector: #include <vector> #include <cstdio> class A { int *array; int size; public: A(int s) { array = new int[size = s]; fprintf(stderr, "Allocated %p\n", (void*)array); } ~A() { fprintf(stderr, "Deleting %p\n", (void*)array); delete array; } }; int main() { std::vector<A> v; for (int n = 0; n < 10; n++) { fprintf(stderr, "Adding object %d\n", n); v.push_back(A(10 * n)); //v.emplace_back(10 * n); } return 0; } When I run this program, it crashes

问题 For simplicity, I'll stick to vector<int> but I think this applies to any vector<T> object. If I am using a vector<int>::iterator to keep track of some position in a vector of int's and then I use vector<int>::push_back() , the iterator becomes worthless. Meaning, I can't take its address with & or dereference it. The direct reason made sense once I printed the address of some of the objects in the following sense: vector<int> my_vec(1); //my_vec[0] = 0 vector<int>::iterator it = my_vec.begin

问题 I am sorry. I wasn't clair previously. I have a file that include data in the following format A(3) B(4),A C(2),A E(5),A G(3),A J(8),B,H H(7),C,E,G I(6),G F(5),H ... These data represent a graph. I will use the critical path method to calculate how to get through this text file. the char is the step the int is the length of each task the other char is step that come before the first char So I have created the class Task to read the file and its constructor have the following parameters Tache:

问题 I am a novice programmer and this is my second question on Stack Overflow. I am trying to implement a pushback function for my Linked List by using a tail pointer. It seems straightforward enough, but I have a nagging feeling that I am forgetting something or that my logic is screwy. Linked Lists are hard! Here is my code: template <typename T> void LinkedList<T>::push_back(const T n) { Node *newNode; // Points to a newly allocated node // A new node is created and the value that was passed

问题 I am trying to speed vector::push_back when capacity cant be predicted When reserve is available a vector push_back writes the new element at the end of the container, and then the end marker is moved. After all reserve is used, push_back may trigger reallocation which is a slow process. To speed this up, reserve is regenerated for several coming push_back without reallocation when empty. How do you think this code assist in achieving that goal ? #ifndef __VECTOR_HPP #define __VECTOR_HPP

问题 vector <int> col(0); vector<vector<int> > row(0); for(i=0;i<10;i++) col.push_back(some integer); row.push_back(col); col.clear(); Can someone tell me what is wrong here? In the col[] vector, there is no error, but when I go to the next instruction by debug on line the before last line, just size of row[] changes to 1 from 0, but I can't see the values that it should take from the col[] vector? Edit: I tried to put debug screen's screen-shot but reputation thing happened. 回答1: There is

问题 I've been scratching my head for far too long, I'm finding using MPL very difficult to get around and hoping somebody can get me started. Here is some partial code from a class I am developing which does not use MPL. I eventually want to implement this class all at compile time. This code probably won't make sense but I don't want all the solution in MPL - hopefully I can achieve that myself (see below for particular help). class define_cell_type{ public: define_cell_type () = default; define