std::map和std::mulitmap的简单实现

template <class Pair>
struct Select1st_
{
    const typename Pair::first_type& operator()(const Pair& x) const
    {
        return x.first;
    }
};
template <class Key, class Tp, class Compare = std::less<Key>>
class Mymap
{
    typedef Key                   key_type;
    typedef Tp                    data_type;
    typedef std::pair<Key, Tp>    value_type;
private:
    typedef Rb_tree<key_type, value_type, Select1st_<value_type>, Compare> Rep_type;
    Rep_type m_rbtree;
public:
    typedef typename Rep_type::iterator iterator;
    typedef typename Rep_type::size_type size_type;
    Mymap() : m_rbtree() {}
    Mymap(Mymap&& x) : m_rbtree(std::move(x.m_rbtree)) {}
    iterator begin() { return m_rbtree.begin(); }
    iterator end() { return m_rbtree.end(); }
    bool empty() const { return m_rbtree.empty(); }
    size_type size() const { return m_rbtree.size(); }
    
    Tp& operator[](const key_type& k)
    {// 如果下标key值不存在，就新插入一个默认构造值
        iterator i = m_rbtree.lower_bound(k);
        if (i == end() || Compare()(k, (*i).first))
        {
            std::pair<iterator, bool> ret =  insert(value_type(k, Tp()));
            return (*(ret.first)).second;
        }
        return (*i).second;
    }
    void swap(Mymap& x) { m_rbtree.swap(x.m_rbtree); }

    std::pair<iterator, bool> insert(const value_type& x)
    {
        return m_rbtree.insert_unique(x);
    }
    void erase(iterator position) { m_rbtree.erase(position); }
    size_type erase(const key_type& x) { return m_rbtree.erase(x); }
    void clear() { m_rbtree.clear(); }
    iterator find(const key_type& x) { return m_rbtree.find(x); }
    size_type count(const key_type& x) const
    {
        return m_rbtree.count(x);
    }
    iterator lower_bound(const key_type& x) { return m_rbtree.lower_bound(x); }
    iterator upper_bound(const key_type& x) { return m_rbtree.upper_bound(x); }
};

template <class Key, class Tp, class Compare = std::less<Key>>
class Mymultimap
{
public:
    typedef Key                   key_type;
    typedef Tp                    data_type;
    typedef std::pair<Key, Tp>    value_type;

private:
    typedef Rb_tree<key_type, value_type, Select1st_<value_type>, Compare> Rep_type;
    Rep_type m_rbtree;
public:
    typedef typename Rep_type::iterator iterator;
    typedef typename Rep_type::size_type size_type;
    Mymultimap() : m_rbtree() {}
    Mymultimap(Mymultimap&& x) : m_rbtree(std::move(x.m_rbtree)) {}

    iterator begin() { return m_rbtree.begin(); }
    iterator end() { return m_rbtree.end(); }
    bool empty() const { return m_rbtree.empty(); }
    size_type size() const { return m_rbtree.size(); }
    void swap(Mymultimap& x) { m_rbtree.swap(x.m_rbtree); }

    iterator insert(const value_type& x) { return m_rbtree.insert_equal(x); }
    void erase(iterator position) { m_rbtree.erase(position); }
    size_type erase(const key_type& x) { return m_rbtree.erase(x); }
    void clear() { m_rbtree.clear(); }
    iterator find(const key_type& x) { return m_rbtree.find(x); }
    size_type count(const key_type& x) const { return m_rbtree.count(x); }
};