1. Multiset Class and its Iterator
The multiset class is a container class in the Standard Template Library (STL)
Include a feature called the iterator, which permits a programmer to easily step through all the elements of an STL container class.
Data Structures
and Other Objects
Using C++

2. Multiset and Set classes
Multiset is similar to bag
Set has the same interface as the multiset, except that it stores elements without repetition

3. Multiset example Template instantiation multiset<int> first;
first.insert(8);
fisrt.insert(4);
first.insert(4);
Template instantiation

4. Multiset restriction
The type of item in a multiset must be possible to compare two items using “<” operator
Satisfy the rules of a strict weak ordering

5. Multiset members value_type size_type
size_type count(const value_type& target) const;
size_type erase(const value_type& target);
size_type size( ) const;
iterator insert(const value_type& entry);

6. Iterators
An iterator is an object that permits a programmer to easily step through all the items in a container, examining the items changing them.
Member functions:
begin
end * ++

7. begin member function
Its return value is an iterator that provides access to the first item in the container
multiset<string> actors;
multiset<string>::iterator role;
role = actors.begin();

8. end member function
Its return value is an iterator that provides access to the last item in the container
multiset<string> actors;
multiset<string>::iterator role;
role = actors.end();

9. * operator
The * operator can be used to access (cannot change) the current element of the iterator
multiset<string> actors;
multiset<string>::iterator role;
role = actors.begin();
cout<< *role <<endl;

10. ++ operator
++ operator can be used to move an iterator forward to the item in its collection
multiset<string> actors;
multiset<string>::iterator role;
role = actors.begin();
++role;

11. The [ … )Pattern

12. Pitfall Do not access an iterator’s item after reaching end()
Remember end() is one location past the last item of the container

13. Other multiset operations!= ==
It is an error to compare two iterators from different containers
find
erase
multiset<int> m;
multiset<int>::iterator position;
position = m.find(42);
if(position != m.end())
m.erase(position);