The multimap::empty() is a boolean type observer function in C++ STL which tells whether the container is empty or not. This function returns true when the multimap container is empty (i.e. the size of the container is 0). Being an observer function it does not modify the multimap in any way.
Syntax:
multimap1.empty()
Return Value: This method returns a boolean type value. It returns true when multimap is empty else returns false.
Below program illustrate the multimap::empty() function:
CPP
// C++ program to demonstrate // std::multimap::empty #include <iostream> #include <map> using namespace std;
int main()
{ // declaring multimap
multimap< char , int > mmap;
// checking if mmap is empty or not
if (mmap.empty())
cout << "multimap is empty\n" ;
// inserting values to mmap
// thus making it non empty
mmap.insert(pair< char , int >( 'a' , 26));
mmap.insert(pair< char , int >( 'b' , 30));
mmap.insert(pair< char , int >( 'c' , 44));
// checking that mmap is now not empty
if (mmap.empty())
cout << "multimap is empty\n" ;
else
cout << "multimap is not empty\n" ;
return 0;
} |
Output:
multimap is empty multimap is not empty
Time Complexity : O(1)