C++ Unordered_multimap Library - size() Function

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Description

The C++ function std::unordered_multimap::size() returns the number of elements present in the unordered_multimap.

Declaration

Following is the declaration for std::unordered_multimap::size() function form std::unordered_map() header.

C++11

size_type size() const noexcept;

Parameters

None

Return value

Returns the actual objects present in unordered_multimap.

Exceptions

This member function never throws exception.

Time complexity

Constant i.e. O(1)

Example

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

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_multimap<char, int> umm; 

   cout << "Initial size of unordered multimap = " << umm.size()
        << endl;

   umm = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5},
            };

   cout << "Size of unordered multimap after insertion = " << umm.size()
        << endl;

   return 0;
}

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

Initial size of unordered multimap = 0
Size of unordered multimap after insertion = 5