Description : This function is used to return size of an unordered map.
Example :
// Demonstrates size()
#include <iostream>
#include <unordered_map>
int main(){
//declares an empty map. O(1)
std::unordered_map<char, int> mymap;
//print size of mymap before inserting key and value in unordered_map
std::cout << "mymap size is = " <<mymap.size()<< '\n';
//inserting in to unordered_map with O(1) time on average
mymap.insert({'A', 1});
mymap.insert({'b', 2});
mymap.insert({'c', 3});
//print size of mymap After inserting key and value in unordered_map
std::cout << "mymap size is = " <<mymap.size()<< '\n';
return 0;
}