C++ Map Library - empty() Function

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Description

The C++ function std::multimap::empty() tests whether multimap is empty or not. Multimap of size zero is considered as empty.

Declaration

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

C++98

bool empty() const;

C++11

bool empty() const noexcept;

Parameters

None

Return value

Returns true if multimap is empty otherwise false.

Exceptions

This member function never throws exception.

Time complexity

Constant i.e. O(1)

Example

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

#include <iostream>
#include <map>

using namespace std;

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

   if (m.empty())
      cout << "Multimap is empty." << endl;

   m.emplace_hint(m.begin(), 'a', 1);

   if (!m.empty())
      cout << "Multimap is not empty." << endl;

   return 0;
}

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

Multimap is empty.
Multimap is not empty.