title: C++ feature, like std::set, which allows duplicates
body: <p>I have an <code>std::set</code>, which stores <code>std::pair</code>s of two integers. The <code>std::set</code> is also sorted, by allowing me to pass a helping class. However, I have written many lines of code so far and now, at the last tests, "they" told me something, that actually means that I need to allow possible duplicates in the <code>std::set</code>. Of course this isn't done with <code>std::set</code>. Any alternative that will not make me change the whole-big project?</p>
  
  <p>In short, I use the <code>std::set</code> as an ordered list with data an <code>std::pair</code> of two ints.</p>