Library: Containers
Does not inherit
An associative container that allows fast access to stored key values. Storage of duplicate keys is allowed. A multiset supports bidirectional iterators.
#include <set>
namespace std {
template <class Key, class Compare = less<Key>,
class Allocator = allocator<Key> >
class multiset;
}
multiset allows fast access to stored key values. The default operation for key comparison is the < operator. Insertion of duplicate keys is allowed with a multiset.
multiset uses bidirectional iterators that point to a stored key.
Any type used for the template parameter Key must include the following (where T is the type, t is a value of T and u is a const value of T):
Copy constructors |
T(t) and T(u) |
Destructor |
t.~T() |
Address of |
&t and &u yielding T* and const T* respectively |
Assignment |
t = a where a is a (possibly const) value of T |
The type used for the Compare template parameter must satisfy the requirements for binary functions.
namespace std {
template <class Key, class Compare = less<Key>,
class Allocator = allocator<Key> >
class multiset {
public:
// typedefs
typedef Key key_type;
typedef Key value_type;
typedef Compare key_compare;
typedef Compare value_compare;
typedef Allocator allocator_type;
typedef typename
Allocator::reference reference;
typedef typename
Allocator::const_reference const_reference;
class iterator;
class const_iterator;
typedef typename
Allocator::size_type size_type;
typedef typename
Allocator::difference_type difference_type;
typedef typename Allocator::pointer pointer;
typedef typename Allocator::const_pointer const_pointer;
typedef typename std::reverse_iterator<iterator>
reverse_iterator;
typedef typename std::reverse_iterator<const_iterator>
const_reverse_iterator;
// Construct/Copy/Destroy
explicit multiset(const Compare& = Compare(),
const Allocator& = Allocator());
template <class InputIterator>
multiset(InputIterator, InputIterator,
const Compare& = Compare(),
const Allocator& = Allocator());
multiset(const multiset<Key, Compare, Allocator>&);
~multiset();
multiset<Key, Compare, Allocator>&
operator=(const multiset<Key,
Compare, Allocator>&);
// Iterators
iterator begin();
const_iterator begin() const;
iterator end();
const_iterator end() const;
reverse_iterator rbegin();
const_reverse_iterator rbegin() const;
reverse_iterator rend();
const_reverse_iterator rend() const;
// Capacity
bool empty() const;
size_type size() const;
size_type max_size() const;
// Modifiers
iterator insert(const value_type&);
iterator insert(iterator, const value_type&);
template <class InputIterator>
void insert(InputIterator, InputIterator);
void erase(iterator);
size_type erase(const key_type&);
void erase(iterator, iterator);
void swap(multiset<Key, Compare, Allocator>&);
void clear();
// Observers
key_compare key_comp () const;
value_compare value_comp () const;
// Multiset operations
iterator find(const key_type&) const;
size_type count(const key_type&) const;
iterator lower_bound(const key_type&) const;
iterator upper_bound(const key_type&) const;
pair<iterator, iterator> equal_range
(const key_type&) const;
};
// Nonmember Operators
template <class Key, class Compare, class Allocator>
bool operator==
(const multiset<Key, Compare, Allocator>&,
const multiset<Key, Compare, Allocator>&);
template <class Key, class Compare, class Allocator>
bool operator!=
(const multiset<Key, Compare, Allocator>&,
const multiset<Key, Compare, Allocator>&);
template <class Key, class Compare, class Allocator>
bool operator<
(const multiset<Key, Compare, Allocator>&,
const multiset<Key, Compare, Allocator>&);
template <class Key, class Compare, class Allocator>
bool operator>
(const multiset<Key, Compare, Allocator>&,
const multiset<Key, Compare, Allocator>&);
template <class Key, class Compare, class Allocator>
bool operator<=
(const multiset<Key, Compare, Allocator>&,
const multiset<Key, Compare, Allocator>&);
template <class Key, class Compare, class Allocator>
bool operator>=
(const multiset<Key, Compare, Allocator>&,
const multiset<Key, Compare, Allocator>&);
// Specialized Algorithms
template <class Key, class Compare, class Allocator>
void swap(multiset<Key, Compare, Allocator>&,
multiset<Key, Compare, Allocator>&);
}
explicit multiset(const Compare& comp = Compare(),
const Allocator& alloc = Allocator());
Constructs an empty multiset that uses the optional relation comp to order keys, if it is supplied, and the allocator alloc for all storage management.
template <class InputIterator>
multiset(InputIterator start, InputIterator finish,
const Compare& = Compare(),
const Allocator& = Allocator());
Constructs a multiset containing values in the range [start, finish).
multiset(const multiset<Key, Compare, Allocator>& x);
Creates a new multiset by copying all key values from x.
~multiset();
Releases any allocated memory for this multiset.
multiset<Key, Compare, Allocator>& operator=(const multiset<Key, Compare, Allocator>& x);
Replaces the contents of *this with a copy of the contents of x.
allocator_type get_allocator() const;
Returns a copy of the allocator used by self for storage management.
iterator begin();
Returns an iterator pointing to the first element stored in the multiset. "First" is defined by the multiset's comparison operator, Compare.
const_iterator begin();
Returns a const_iterator pointing to the first element stored in the multiset.
iterator end();
Returns an iterator pointing to the last element stored in the multiset (in other words, the off-the-end value).
const_iterator end();
Returns a const_iterator pointing to the last element stored in the multiset (in other words, the off-the-end value).
reverse_iterator rbegin();
Returns a reverse_iterator pointing to the first element stored in the multiset. "First" is defined by the multiset's comparison operator, Compare.
const_reverse_iterator rbegin();
Returns a const_reverse_iterator pointing to the first element stored in the multiset.
reverse_iterator rend();
Returns a reverse_iterator pointing to the last element stored in the multiset (in other words, the off-the-end value).
const_reverse_iterator rend();
Returns a const_reverse_iterator pointing to the last element stored in the multiset (in other words, the off-the-end value).
void clear();
Erases all elements from the self.
size_type count(const key_type& x) const;
Returns the number of elements in the multiset with the key value x.
bool empty() const;
Returns true if the multiset is empty, false otherwise.
pair<iterator,iterator> equal_range(const key_type& x)const;
Returns the pair (lower_bound(x), upper_bound(x)).
size_type erase(const key_type& x);
Deletes all elements with the key value x from the multiset, if any exist. Returns the number of deleted elements.
void erase(iterator position);
Deletes the multiset element pointed to by the iterator position.
void erase(iterator start, iterator finish);
If the iterators start and finish point to the same multiset and last is reachable from first, all elements in the range [start, finish) are deleted from the multiset.
iterator find(const key_type& x) const;
Searches the multiset for a key value x and returns an iterator to that key if it is found. If such a value is not found, the iterator end() is returned.
iterator insert(const value_type& x); iterator insert(iterator position, const value_type& x);
x is inserted into the multiset. A position may be supplied as a hint regarding where to do the insertion. If the insertion is done right after position, then it takes amortized constant time. Otherwise, it takes O(log N) time.
template <class InputIterator> void insert(InputIterator start, InputIterator finish);
Copies of each element in the range [start, finish) are inserted into the multiset. This insert takes approximately O(N*log(size()+N)) time.
key_compare key_comp() const;
Returns a function object capable of comparing key values using the comparison operation, Compare, of the current multiset.
iterator lower_bound(const key_type& x) const;
Returns an iterator to the first element whose key is greater than or equal to x. If no such element exists, end() is returned.
size_type max_size() const;
Returns the maximum possible size of the multiset size_type.
size_type size() const;
Returns the number of elements in the multiset.
void swap(multiset<Key, Compare, Allocator>& x);
Swaps the contents of the multiset x with the current multiset, *this.
iterator upper_bound(const key_type& x) const;
Returns an iterator to the first element whose key is smaller than or equal to x. If no such element exists, then end() is returned.
value_compare value_comp() const;
Returns a function object capable of comparing key values using the comparison operation, Compare, of the current multiset.
template <class Key, class Compare, class Allocator>
operator==(const multiset<Key, Compare, Allocator>& x,
const multiset<Key, Compare, Allocator>& y);
Returns true if all elements in x are element-wise equal to all elements in y, using (T::operator==). Otherwise it returns false.
template <class Key, class Compare, class Allocator>
operator!=(const multiset<Key, Compare, Allocator>& x,
const multiset<Key, Compare, Allocator>& y);
Returns !(x==y).
template <class Key, class Compare, class Allocator>
operator<(const multiset<Key, Compare, Allocator>& x,
const multiset<Key, Compare, Allocator>& y);
Returns true if x is lexicographically less than y. Otherwise, it returns false.
template <class Key, class Compare, class Allocator>
operator>(const multiset<Key, Compare, Allocator>& x,
const multiset<Key, Compare, Allocator>& y);
Returns y < x.
template <class Key, class Compare, class Allocator>
operator<=(const multiset<Key, Compare, Allocator>& x,
const multiset<Key, Compare, Allocator>& y);
Returns !(y < x).
template <class Key, class Compare, class Allocator>
operator>=(const multiset<Key, Compare, Allocator>& x,
const multiset<Key, Compare, Allocator>& y);
Returns !(x < y).
template <class Key, class Compare, class Allocator>
void swap(multiset<Key,Compare,Allocator>& a,
multiset<Key,Compare,Allocator>&b);
Swaps the contents of a and b.
//
// multiset.cpp
//
#include <algorithm> // for set_intersection, set_union
#include <iostream> // for cout, endl
#include <set> // for set
typedef std::multiset<int, std::less<int>,
std::allocator<int> > set_type;
inline std::ostream& operator<< (std::ostream& out,
const set_type& s)
{
typedef std::ostream_iterator<set_type::value_type, char,
std::char_traits<char> > os_iter;
std::copy (s.begin (), s.end (), os_iter (std::cout, " "));
return out;
}
int main ()
{
// Create a multiset of integers.
set_type si;
for (set_type::value_type j = 0; j < 2; j++) {
for (set_type::value_type i = 0; i < 10; ++i)
// Insert values with a hint.
si.insert (si.begin (), i);
}
// Print out the multiset.
std::cout << si << std::endl;
// Make another multiset and an empty multiset.
set_type si2, result;
for (set_type::value_type i = 0; i < 10; i++)
si2.insert (i + 5);
std::cout << si2 << std::endl;
// Try a couple of set algorithms.
std::set_union (si.begin (), si.end (),
si2.begin (), si2.end (),
std::inserter (result, result.begin ()));
std::cout << "Union:\n" << result << std::endl;
result.erase (result.begin (), result.end ());
std::set_intersection (si.begin (), si.end (),
si2.begin (), si2.end (),
std::inserter(result, result.begin()));
std::cout << "Intersection:\n" << result << std::endl;
return 0;
}
Program Output:
0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 5 6 7 8 9 10 11 12 13 14 Union: 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 11 12 13 14 Intersection: 5 6 7 8 9
Member function templates are used in all containers included in the Standard Template Library. For example, the constructor for multiset takes two templatized iterators:
template <class InputIterator>
multiset (InputIterator, InputIterator,
const Compare& = Compare(),
const Allocator& = Allocator());
multiset also has an insert function of this type. These functions, when not restricted by compiler limitations, allow you to use any type of input iterator as arguments. For compilers that do not support this feature, substitute functions allow you to use an iterator obtained from the same type of container as the one you are constructing (or calling a member function on). You can also use a pointer to the type of element you have in the container.
For example, if your compiler does not support member function templates, you can construct a multiset in the following two ways:
int intarray[10];
multiset<int> first_multiset(intarray, intarray +10);
multiset<int> second_multiset(first_multiset.begin(),
first_multiset.end());
You cannot construct a multiset this way:
multiset<long> long_multiset(first_multiset.begin(),first_multiset.end());
since the long_multiset and first_multiset are not the same type.
If your compiler is does not support default template parameters, you must always supply the Compare template argument and the Allocator template argument. For instance, you must write:
multiset<int, less<int>, allocator<int> >
instead of:
multiset<int>
allocator, Containers, Iterators, set
ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 23.3.4