How to select a random element in std::set?

Question

How can I select a random element in an std::set?

I naively tried this:

int GetSample(const std::set& s) {
  double r =          


        

Answer 1

You could use the std::advance method.

#include 
#include 

int main() {
  using namespace std;
  // generate a set...
  set s;
  for( int i = 0; i != 10; ++i ) s.insert(i);
  auto r = rand() % s.size(); // not _really_ random
  auto n = *select_random(s, r);
}

Where

template
auto select_random(const S &s, size_t n) {
  auto it = std::begin(s);
  // 'advance' the iterator n times
  std::advance(it,n);
  return it;
}