C / C++ / MFC

multiset<double> s;
multiset<double>::iterator it;

it = s.begin();

for (int i = 0; i < s.size(); ++i)
  it++;

it += k;

alikalik wrote:

Or maybe other data stuctures like Map would be better for this task?

template<class Type>
class SortedVector
{
public:
   SortedVector() sorted_(true) {}
   void insert(Type const& value)
   {
      sorted_ = false;
      data_.push_back(value);
   }
   typename std::vector<Type>::const_iterator find(Type const& value) const
   {
      if (!sorted_)
      {
         std::sort(data_.begin(), data_.end());
         sorted_ = true;
      }
      std::vector<Type>::const_iterator found = 
            std::lower_bound(data_.begin(), data_.end(), value);
      return (*found == value)?found:data_.end();
   }
private:
   mutable bool sorted_;
   mutable std::vector<Type> data_;
};