5.5 multiset

       multiset的特性及其用法和set完全相同，唯一的区别就是multiset允许键值key重复，因此multiset的插入操作采用的是底层RB-Tree的insert_equal()(可以插入重复的键)而非insert_unique()。本文的源码出自SGI
STL中的<stl_multiset.h>文件。

#ifndef __SGI_STL_INTERNAL_MULTISET_H
#define __SGI_STL_INTERNAL_MULTISET_H
 
#include <concept_checks.h>
 
__STL_BEGIN_NAMESPACE
 
#if defined(__sgi) &&!defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1174
#pragma set woff 1375
#endif
 
//multiset的特性及其用法和set完全相同，唯一的区别就是multiset允许键值key重复
//因此multiset的插入操作采用的是底层RB-Tree的insert_equal()而非insert_unique()
//有关set容器的剖析见前面博文
 
// Forward declaration of operators <and ==, needed for friend declaration.
 
//multiset内部元素默认使用递增排序less
//用户可自行制定比较类型
//内部维护的数据结构是红黑树, 具有非常优秀的最坏情况的时间复杂度
template <class _Key, class _Compare__STL_DEPENDENT_DEFAULT_TMPL(less<_Key>),
         class _Alloc = __STL_DEFAULT_ALLOCATOR(_Key) >
class multiset;
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator==(constmultiset<_Key,_Compare,_Alloc>& __x,
                       constmultiset<_Key,_Compare,_Alloc>& __y);
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator<(constmultiset<_Key,_Compare,_Alloc>& __x,
                      constmultiset<_Key,_Compare,_Alloc>& __y);
 
template <class _Key, class _Compare,class _Alloc>
class multiset {
  //requirements:
 
 __STL_CLASS_REQUIRES(_Key, _Assignable);
 __STL_CLASS_BINARY_FUNCTION_CHECK(_Compare, bool, _Key, _Key);
 
public:
 
  //typedefs:
 
  //以下的定义与set相同
 typedef _Key     key_type;
 typedef _Key     value_type;
 typedef _Compare key_compare;
 typedef _Compare value_compare;
private:
         //底层机制是采用RB-Tree
  typedef_Rb_tree<key_type, value_type,
                  _Identity<value_type>,key_compare, _Alloc> _Rep_type;
 _Rep_type _M_t;  // red-black treerepresenting multiset
public:
 typedef typename _Rep_type::const_pointer pointer;
 typedef typename _Rep_type::const_pointer const_pointer;
 typedef typename _Rep_type::const_reference reference;
 typedef typename _Rep_type::const_reference const_reference;
 typedef typename _Rep_type::const_iterator iterator;
 typedef typename _Rep_type::const_iterator const_iterator;
 typedef typename _Rep_type::const_reverse_iterator reverse_iterator;
 typedef typename _Rep_type::const_reverse_iteratorconst_reverse_iterator;
 typedef typename _Rep_type::size_type size_type;
 typedef typename _Rep_type::difference_type difference_type;
 typedef typename _Rep_type::allocator_type allocator_type;
 
  //allocation/deallocation
  /*
  构造函数
                   multiset();
                   explicitmultiset (const key_compare& comp = key_compare(),
                                                  const allocator_type& alloc =allocator_type());
                  
                   template<class InputIterator>
                   multiset(InputIterator first, InputIterator last,
                                     constkey_compare& comp = key_compare(),
                                     constallocator_type& alloc = allocator_type());
                  
                   multiset(const multiset& x);
  */
 
 multiset() : _M_t(_Compare(), allocator_type()) {}
 explicit multiset(const _Compare& __comp,
                    const allocator_type&__a = allocator_type())
    :_M_t(__comp, __a) {}
 
#ifdef __STL_MEMBER_TEMPLATES
 
 //multiset的插入操作采用的是底层RB-Tree的insert_equal()而非insert_unique()
 template <class _InputIterator>
 multiset(_InputIterator __first, _InputIterator __last)
    :_M_t(_Compare(), allocator_type())
    {_M_t.insert_equal(__first, __last); }
 
 template <class _InputIterator>
 multiset(_InputIterator __first, _InputIterator __last,
          const _Compare& __comp,
          const allocator_type& __a = allocator_type())
    :_M_t(__comp, __a) { _M_t.insert_equal(__first, __last); }
 
#else
 
 multiset(const value_type* __first, const value_type* __last)
    :_M_t(_Compare(), allocator_type())
    {_M_t.insert_equal(__first, __last); }
 
 multiset(const value_type* __first, const value_type* __last,
          const _Compare& __comp,
          const allocator_type& __a = allocator_type())
    :_M_t(__comp, __a) { _M_t.insert_equal(__first, __last); }
 
 multiset(const_iterator __first, const_iterator __last)
    :_M_t(_Compare(), allocator_type())
    {_M_t.insert_equal(__first, __last); }
 
 multiset(const_iterator __first, const_iterator __last,
          const _Compare& __comp,
          const allocator_type& __a = allocator_type())
    :_M_t(__comp, __a) { _M_t.insert_equal(__first, __last); }
  
#endif /* __STL_MEMBER_TEMPLATES */
 
  multiset(constmultiset<_Key,_Compare,_Alloc>& __x) : _M_t(__x._M_t) {}
 multiset<_Key,_Compare,_Alloc>&
 operator=(const multiset<_Key,_Compare,_Alloc>& __x) {
   _M_t = __x._M_t;//调用了底层红黑树的operator=操作函数
   return *this;
  }
 
  //以下所有的multiset操作行为，RB-tree都已提供，所以multiset只要调用即可
  //accessors:
 
  //返回用于key比较的函数,调用RB-Tree的key_comp()
 key_compare key_comp() const { return _M_t.key_comp(); }
   //由于multiset的性质, value和key使用同一个比较函数
 value_compare value_comp() const { return _M_t.key_comp(); }
 allocator_type get_allocator() const { return _M_t.get_allocator(); }
 
 iterator begin() const { return _M_t.begin(); }
 iterator end() const { return _M_t.end(); }
 reverse_iterator rbegin() const { return _M_t.rbegin(); }
 reverse_iterator rend() const { return _M_t.rend(); }
 bool empty() const { return _M_t.empty(); }
 size_type size() const { return _M_t.size(); }
 size_type max_size() const { return _M_t.max_size(); }
  //这里调用的swap()函数是专属于RB-Tree的swap()，并不是STL的swap()算法
 void swap(multiset<_Key,_Compare,_Alloc>& __x) {_M_t.swap(__x._M_t); }
 
  //insert/erase
  /*
  插入节点
         iteratorinsert (const value_type& val);
        
         iteratorinsert (iterator position, const value_type& val);
                  
         template<class InputIterator>
         voidinsert (InputIterator first, InputIterator last);
  */
  //插入数据节点
 iterator insert(const value_type& __x) {
   return _M_t.insert_equal(__x);
  }
  //在指定位置插入节点
 iterator insert(iterator __position, const value_type& __x) {
   typedef typename _Rep_type::iterator _Rep_iterator;
   return _M_t.insert_equal((_Rep_iterator&)__position, __x);
  }
 
#ifdef __STL_MEMBER_TEMPLATES 
 template <class _InputIterator>
 void insert(_InputIterator __first, _InputIterator __last) {
   _M_t.insert_equal(__first, __last);
  }
#else
 void insert(const value_type* __first, const value_type* __last) {
   _M_t.insert_equal(__first, __last);
  }
 void insert(const_iterator __first, const_iterator __last) {
   _M_t.insert_equal(__first, __last);
  }
#endif /* __STL_MEMBER_TEMPLATES */
  //擦除指定位置的元素
 void erase(iterator __position) {
   typedef typename _Rep_type::iterator _Rep_iterator;
   _M_t.erase((_Rep_iterator&)__position);
  }
  //擦除元素值为x的节点
 size_type erase(const key_type& __x) {
   return _M_t.erase(__x);
  }
  //擦除指定区间的节点
 void erase(iterator __first, iterator __last) {
   typedef typename _Rep_type::iterator _Rep_iterator;
   _M_t.erase((_Rep_iterator&)__first, (_Rep_iterator&)__last);
  }
  //清除multiset
 void clear() { _M_t.clear(); }
 
  //multiset operations:
 
  //查找元素值为x的节点
 iterator find(const key_type& __x) const { return _M_t.find(__x); }
  //返回指定元素的个数
 size_type count(const key_type& __x) const { return _M_t.count(__x);}
 //Returns an iterator pointing to the first element in the container
 //whose key is not considered to go before k (i.e., either it isequivalent or goes after).
 iterator lower_bound(const key_type& __x) const {
   return _M_t.lower_bound(__x);
  }
 //Returns an iterator pointing to the first element that is greater thankey.
 iterator upper_bound(const key_type& __x) const {
   return _M_t.upper_bound(__x);
  }
 //Returns the bounds of a range that includes all the elements in thecontainer
 //which have a key equivalent to k
 //Because the elements in a map container have unique keys,
 //the range returned will contain a single element at most.
 pair<iterator,iterator> equal_range(const key_type& __x) const{
   return _M_t.equal_range(__x);
  }
 
  //以下是操作符的重载
 
#ifdef __STL_TEMPLATE_FRIENDS
 template <class _K1, class _C1, class _A1>
 friend bool operator== (const multiset<_K1,_C1,_A1>&,
                          constmultiset<_K1,_C1,_A1>&);
 template <class _K1, class _C1, class _A1>
 friend bool operator< (const multiset<_K1,_C1,_A1>&,
                         constmultiset<_K1,_C1,_A1>&);
#else /* __STL_TEMPLATE_FRIENDS */
 friend bool __STD_QUALIFIER
 operator== __STL_NULL_TMPL_ARGS (const multiset&, constmultiset&);
 friend bool __STD_QUALIFIER
 operator< __STL_NULL_TMPL_ARGS (const multiset&, constmultiset&);
#endif /* __STL_TEMPLATE_FRIENDS */
};
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator==(constmultiset<_Key,_Compare,_Alloc>& __x,
                      constmultiset<_Key,_Compare,_Alloc>& __y) {
 return __x._M_t == __y._M_t;
}
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator<(constmultiset<_Key,_Compare,_Alloc>& __x,
                      const multiset<_Key,_Compare,_Alloc>&__y) {
 return __x._M_t < __y._M_t;
}
 
#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator!=(constmultiset<_Key,_Compare,_Alloc>& __x,
                       constmultiset<_Key,_Compare,_Alloc>& __y) {
 return !(__x == __y);
}
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator>(constmultiset<_Key,_Compare,_Alloc>& __x,
                      const multiset<_Key,_Compare,_Alloc>&__y) {
 return __y < __x;
}
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator<=(constmultiset<_Key,_Compare,_Alloc>& __x,
                       constmultiset<_Key,_Compare,_Alloc>& __y) {
 return !(__y < __x);
}
 
template <class _Key, class _Compare,class _Alloc>
inline bool operator>=(constmultiset<_Key,_Compare,_Alloc>& __x,
                       constmultiset<_Key,_Compare,_Alloc>& __y) {
 return !(__x < __y);
}
 
template <class _Key, class _Compare, class_Alloc>
inline voidswap(multiset<_Key,_Compare,_Alloc>& __x,
                multiset<_Key,_Compare,_Alloc>& __y) {
 __x.swap(__y);
}
 
#endif /* __STL_FUNCTION_TMPL_PARTIAL_ORDER*/
 
#if defined(__sgi) &&!defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma reset woff 1174
#pragma reset woff 1375
#endif
 
__STL_END_NAMESPACE
 
#endif /* __SGI_STL_INTERNAL_MULTISET_H */
 
// Local Variables:
// mode:C++
// End: