Best way to extract a subvector from a vector?
It’s an O(N) operation to construct the new vector, but there isn’t really a better way.
c++
c++ convert string to hex
Use std:stoi as (in C++11 only): Online demo
What’s the most efficient way to erase duplicates and sort a vector?
I agree with R. Pate and Todd Gardner; a std::set might be a good idea here. Even if you’re stuck using vectors, if you have enough duplicates, you might be better off creating a set to do the dirty work. Let’s compare three approaches: Just using vector, sort + unique Convert to set (manually) Convert to set (using a constructor) … Read more
2D array vs array of arrays
A 2 dimensional array is by definition an array of arrays. What Dave was saying is that in that context, there are different semantics between the definition of a 2D array like this: this: or this:
pthread sleep linux
Just the thread. The POSIX documentation for sleep() says: The sleep() function shall cause the calling thread to be suspended from execution…
Is the sizeof(some pointer) always equal to four?
he guarantee you get is that sizeof(char) == 1. There are no other guarantees, including no guarantee that sizeof(int *) == sizeof(double *). In practice, pointers will be size 2 on a 16-bit system (if you can find one), 4 on a 32-bit system, and 8 on a 64-bit system, but there’s nothing to be gained in … Read more
How to get current timestamp in milliseconds since 1970 just the way Java gets
If you have access to the C++ 11 libraries, check out the std::chrono library. You can use it to get the milliseconds since the Unix Epoch like this:
How do I compile C++ to JavaScript in a browser?
In theory, it may be possible to develop a self-hosting version of Emscripten that runs in a browser, though this hasn’t been done yet. Alternatively, it is possible to run a C++ compiler (or even an entire operating system) using an x86 emulator in JavaScript.
error: overloaded ‘operator<<' must be a binary operator (has 3 parameters)
The problem is that you declared operator>> and operator<< as non-member functions, but defined as a member function. This should fix that problem (but open another set of problems). So instead of implement as : Also, take a note that you declared functions as : but defined as (therefore you changed the signature) : Proper way is to declare … Read more
How to dynamically allocate an array of pointers in C++?
But as usual, you are probably better off using a std::vector of pointers.