Question

How do I check for the empty intersection of two std::sets? I can use set_intersection, but that’s unnecessarily slow, I need only bool answer.

Remark: std::set means ordered sets, they are of the same type etc.

Answer 1

Anything wrong with just coding it yourself?

bool empty_intersection(const set<int>& x, const set<int>& y)
{
    set<int>::const_iterator i = x.begin();
    set<int>::const_iterator j = y.begin();
    while (i != x.end() && j != y.end())
    {
      if (*i == *j)
        return false;
      else if (*i < *j)
        ++i;
      else
        ++j;
    }
    return true;
}

Something like that anyway. Completely untested code.