Fastest container or algorithm for unique reusable ids in C++

Question

I have a need for unique reusable ids. The user can choose his own ids or he can ask for a free one. The API is basically

class IdManager {
public:
  int Allocat         


        

Answer 1

Similar to skwllsp, I'd keep track of the ranges that have not been allocated, but my methods are slightly different. The base container would be a map, with the key being the upper bound of the range and the value being the lower bound.

IdManager::IdManager()
{
    m_map.insert(std::make_pair(std::numeric_limits::max(), 1);
}

int IdManager::AllocateId()
{
    assert(!m_map.empty());
    MyMap::iterator p = m_map.begin();
    int id = p->second;
    ++p->second;
    if (p->second > p->first)
        m_map.erase(p);
    return id;
}

void IdManager::FreeId(int id)
{
    // I'll fill this in later
}

bool IdManager::MarkAsUsed(int id)
{
    MyMap::iterator p = m_map.lower_bound(id);

    // return false if the ID is already allocated
    if (p == m_map.end() || id < p->second || id > p->first)))
        return false;

    // first thunderstorm of the season, I'll leave this for now before the power glitches
}

bool IdManager::IsUsed(int id)
{
    MyMap::iterator p = m_map.lower_bound(id);
    return (p != m_map.end() && id >= p->second && id <= p->first);
}