STL中的set不允许键值重复，因此就有了multiset。multiset和set操作一样，功能一样，但是multiset允许键值重复，在使用红黑树的插入操作是，用的是insert_equal，而set用的是insert_unique，其他代码一样。
G++ 2.91.57，cygnus\cygwin-b20\include\g++\stl_multiset.h 完整列表
/*
*
* Copyright (c) 1994
* Hewlett-Packard Company
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Hewlett-Packard Company makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*
*
* Copyright (c) 1996
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
/* NOTE: This is an internal header file, included by other STL headers.
* You should not attempt to use it directly.
*/
#ifndef __SGI_STL_INTERNAL_MULTISET_H
#define __SGI_STL_INTERNAL_MULTISET_H
__STL_BEGIN_NAMESPACE
#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1174
#endif
#ifndef __STL_LIMITED_DEFAULT_TEMPLATES
template <class Key, class Compare = less<Key>, class Alloc = alloc>
#else
template <class Key, class Compare, class Alloc = alloc>
#endif
class multiset {
public:
// typedefs:
typedef Key key_type;
typedef Key value_type;
typedef Compare key_compare;
typedef Compare value_compare;
private:
typedef rb_tree<key_type, value_type,
identity<value_type>, key_compare, Alloc> rep_type;
rep_type t; // red-black tree representing 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_iterator const_reverse_iterator;
typedef typename rep_type::size_type size_type;
typedef typename rep_type::difference_type difference_type;
// allocation/deallocation
// 注意， multiset 一定使用 insert_equal() 而不使用 insert_unique()。
// set 才使用 insert_unique()。
multiset() : t(Compare()) {}
explicit multiset(const Compare& comp) : t(comp) {}
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
multiset(InputIterator first, InputIterator last)
: t(Compare()) { t.insert_equal(first, last); }
template <class InputIterator>
multiset(InputIterator first, InputIterator last, const Compare& comp)
: t(comp) { t.insert_equal(first, last); }
#else
multiset(const value_type* first, const value_type* last)
: t(Compare()) { t.insert_equal(first, last); }
multiset(const value_type* first, const value_type* last,
const Compare& comp)
: t(comp) { t.insert_equal(first, last); }
multiset(const_iterator first, const_iterator last)
: t(Compare()) { t.insert_equal(first, last); }
multiset(const_iterator first, const_iterator last, const Compare& comp)
: t(comp) { t.insert_equal(first, last); }
#endif /* __STL_MEMBER_TEMPLATES */
multiset(const multiset<Key, Compare, Alloc>& x) : t(x.t) {}
multiset<Key, Compare, Alloc>&
operator=(const multiset<Key, Compare, Alloc>& x) {
t = x.t;
return *this;
}
// accessors:
key_compare key_comp() const { return t.key_comp(); }
value_compare value_comp() const { return t.key_comp(); }
iterator begin() const { return t.begin(); }
iterator end() const { return t.end(); }
reverse_iterator rbegin() const { return t.rbegin(); }
reverse_iterator rend() const { return t.rend(); }
bool empty() const { return t.empty(); }
size_type size() const { return t.size(); }
size_type max_size() const { return t.max_size(); }
void swap(multiset<Key, Compare, Alloc>& x) { t.swap(x.t); }
// insert/erase
iterator insert(const value_type& x) {
return t.insert_equal(x);
}
iterator insert(iterator position, const value_type& x) {
typedef typename rep_type::iterator rep_iterator;
return t.insert_equal((rep_iterator&)position, x);
}
#ifdef __STL_MEMBER_TEMPLATES
template <class InputIterator>
void insert(InputIterator first, InputIterator last) {
t.insert_equal(first, last);
}
#else
void insert(const value_type* first, const value_type* last) {
t.insert_equal(first, last);
}
void insert(const_iterator first, const_iterator last) {
t.insert_equal(first, last);
}
#endif /* __STL_MEMBER_TEMPLATES */
void erase(iterator position) {
typedef typename rep_type::iterator rep_iterator;
t.erase((rep_iterator&)position);
}
size_type erase(const key_type& x) {
return t.erase(x);
}
void erase(iterator first, iterator last) {
typedef typename rep_type::iterator rep_iterator;
t.erase((rep_iterator&)first, (rep_iterator&)last);
}
void clear() { t.clear(); }
// multiset operations:
iterator find(const key_type& x) const { return t.find(x); }
size_type count(const key_type& x) const { return t.count(x); }
iterator lower_bound(const key_type& x) const {
return t.lower_bound(x);
}
iterator upper_bound(const key_type& x) const {
return t.upper_bound(x);
}
pair<iterator,iterator> equal_range(const key_type& x) const {
return t.equal_range(x);
}
friend bool operator== __STL_NULL_TMPL_ARGS (const multiset&,
const multiset&);
friend bool operator< __STL_NULL_TMPL_ARGS (const multiset&,
const multiset&);
};
template <class Key, class Compare, class Alloc>
inline bool operator==(const multiset<Key, Compare, Alloc>& x,
const multiset<Key, Compare, Alloc>& y) {
return x.t == y.t;
}
template <class Key, class Compare, class Alloc>
inline bool operator<(const multiset<Key, Compare, Alloc>& x,
const multiset<Key, Compare, Alloc>& y) {
return x.t < y.t;
}
#ifdef __STL_FUNCTION_TMPL_PARTIAL_ORDER
template <class Key, class Compare, class Alloc>
inline void swap(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
#endif
__STL_END_NAMESPACE
#endif /* __SGI_STL_INTERNAL_MULTISET_H */
// Local Variables:
// mode:C++
// End:
《STL源码剖析》---stl_multiset.h阅读笔记,布布扣,bubuko.com
《STL源码剖析》---stl_multiset.h阅读笔记
原文地址：http://blog.csdn.net/kangroger/article/details/38635299
