Multimap constructors & destructors


    #include <map>
    multimap( const multimap& m );
    multimap( input_iterator start, input_iterator end );
    multimap( input_iterator start, input_iterator end, const key_compare& cmp );
    explicit multimap( const key_compare& cmp );

Multimaps have several constructors:

The default destructor is called when the multimap should be destroyed.

The template definition of multimaps requires that both a key type and value type be supplied. For example, you can instantiate a multimap that maps strings to integers with this statement:

    multimap<string,int> m;

You can also supply a comparison function and an allocator in the template:

    multimap<string,int,myComp,myAlloc> m;

For example, the following code uses a multimap to associate a series of employee names with numerical IDs:

    multimap<string,int> m;
    int employeeID = 0;
    m.insert( pair<string,int>("Bob Smith",employeeID++) );
    m.insert( pair<string,int>("Bob Thompson",employeeID++) );
    m.insert( pair<string,int>("Bob Smithey",employeeID++) );
    m.insert( pair<string,int>("Bob Smith",employeeID++) );
    cout << "Number of employees named 'Bob Smith': " << m.count("Bob Smith") << endl;
    cout << "Number of employees named 'Bob Thompson': " << m.count("Bob Thompson") << endl;
    cout << "Number of employees named 'Bob Smithey': " << m.count("Bob Smithey") << endl;
    cout << "Employee list: " << endl;
    for( multimap<string, int>::iterator iter = m.begin(); iter != m.end(); ++iter ) {
      cout << " Name: " << iter->first << ", ID #" << iter->second << endl;

When run, the above code produces the following output. Note that the employee list is displayed in alphabetical order, because multimaps are sorted associative containers:

    Number of employees named 'Bob Smith': 2
    Number of employees named 'Bob Thompson': 1
    Number of employees named 'Bob Smithey': 1
    Employee list:
     Name: Bob Smith, ID #0
     Name: Bob Smith, ID #3
     Name: Bob Smithey, ID #2
     Name: Bob Thompson, ID #1

Related Topics: count, insert