I am looking for a generic, reusable way to shuffle a std::vector in C++. This is how I currently do it, but I think it's not very efficient because it needs an intermediate array and it needs to know the item type (DeckCard in this example):
srand(time(NULL));
cards_.clear();
while (temp.size() > 0) {
int idx = rand() % temp.size();
DeckCard* card = temp[idx];
cards_.push_back(card);
temp.erase(temp.begin() + idx);
}
It can be even simpler, seeding can be avoided entirely:
#include <algorithm>
#include <random>
// Given some container `container`...
std::shuffle(container.begin(), container.end(), std::random_device());
This will produce a new shuffle each time the program is run. I also like this approach due to the simplicity of the code.
This works because all we need for std::shuffle is a UniformRandomBitGenerator, whose requirements std::random_device meets.
Note: if shuffling repeatedly, it may be better to store the random_device in a local variable:
std::random_device rd;
std::shuffle(container.begin(), container.end(), rd);
Depending of the standard you have to follow (C++11/C++14/C++17) this "cppreference" page provides pretty good examples: https://en.cppreference.com/w/cpp/algorithm/random_shuffle.