C++ multimap - emplace() Function

The C++ multimap::emplace function is used to insert a new element in the multimap. The insertion of the new element increases the size of the multimap by one. As a multimap is an ordered data container, hence it stores the new element in its respective position to keep the multimap sorted.

Syntax

C++11

template <class... Args>
iterator emplace (Args&&... args);

Parameters

args Arguments forwarded to construct the new element of the mapped type.

Return Value

Returns an iterator pointed to newly added element.

Time Complexity

Logarithmic i.e, Θ(log(n)).

Example:

In the example below, the multimap::emplace function is used to insert a new element in the multimap called MyMMap.

#include <iostream>
#include <map>
using namespace std;
 
int main (){
  multimap<string, string> MyMMap;
  multimap<string, string>::iterator it;

  MyMMap.insert(pair<string, string>("USA", "New York"));
  MyMMap.insert(pair<string, string>("USA", "Washington"));  
  MyMMap.insert(pair<string, string>("CAN", "Toronto"));

  //insert a new element in the MyMMap using emplace function
  MyMMap.emplace("IND", "Delhi");
  MyMMap.emplace("CAN", "Montreal");
  
  cout<<"MyMMap contains:"<<"\n ";
  for(it = MyMMap.begin(); it != MyMMap.end(); ++it)
     cout<<it->first<<" => "<<it->second<<"\n ";

  return 0;
}

The output of the above code will be:

MyMMap contains:
 CAN => Toronto
 CAN => Montreal
 IND => Delhi
 USA => New York
 USA => Washington

❮ C++ <map> Library