C++ Map Library - multimap() Function

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Description

The C++ function std::multimap::multimap() constructs an empty multimap with zero elements.

Declaration

Following is the declaration for std::multimap::multimap() function form std::map header.

C++98

explicit multimap (const key_compare& comp = key_compare(),
                  const allocator_type& alloc = allocator_type());

C++11

explicit multimap (const key_compare& comp = key_compare(),
                   const allocator_type& alloc = allocator_type());
explicit multimap (const allocator_type& alloc);

Parameters

• comp − A binary predicate, which takes two key arguments and returns true if first argument goes before second otherwise false. By default it uses less predicate.

• alloc − The allocator object.

Return value

Constructor never returns value.

Exceptions

No effect on container if exception is thrown.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::multimap::multimap() function.

#include <iostream>
#include <map>

using namespace std;

int main(void) {
   multimap<char, int> m;

   cout << "Size of multimap = " << m.size() << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Size of multimap = 0