std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>::size
Min standard notice:
Returns the number of elements in the container, i.e. std::distance(begin(), end()).
# Declarations
size_type size() const noexcept;
(since C++11)
# Return value
The number of elements in the container.
# Example
#include <cassert>
#include <unordered_map>
int main()
{
std::unordered_multimap<int, char> nums{{1, 'a'}, {1, 'b'}, {2, 'c'}, {2, 'd'}};
assert(nums.size() == 4);
}