C++ multimap - rend() Function

The C++ multimap::rend function returns the reverse iterator pointing to the element preceding the first element (reversed past-the-last element) of the multimap. A reverse iterator iterates in backward direction and increasing it results into moving to the beginning of the multimap container. Similarly, decreasing a reverse iterator results into moving to the end of the multimap container.

Note: Multimap is an ordered data container which implies all its elements are ordered all the time.

reverse_iterator rend();
const_reverse_iterator rend() const;

reverse_iterator rend() noexcept;
const_reverse_iterator rend() const noexcept;

Parameters

No parameter is required.

Return Value

A reverse iterator to the reversed past-the-last element of the sequence container. If the sequence object is constant qualified, the function returns a const_reverse_iterator, else returns an reverse_iterator.

Time Complexity

Constant i.e, Θ(1).

Example:

In the example below, the multimap::rend function returns the reverse iterator pointing to the element preceding the first element of the multimap MyMMap.

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

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

  rit = MyMMap.rend();
  rit--;
  cout<<rit->first<<" => "<<rit->second<<"\n";
  rit--;
  cout<<rit->first<<" => "<<rit->second<<"\n";
  rit--;
  cout<<rit->first<<" => "<<rit->second<<"\n";
  return 0;
}

The output of the above code will be:

CAN => Toronto
CAN => Montreal
IND => Delhi

Example:

Lets see another example of multimap where multimap::rend function is used with multimap::rbegin function to specify a range including all elements of the multimap container.

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

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

  cout<<"MyMMap contains:"<<"\n ";
  for(rit = MyMMap.rbegin(); rit != MyMMap.rend(); ++rit)
    cout<<rit->first<<" => "<<rit->second<<"\n ";

  return 0;
}

The output of the above code will be:

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

❮ C++ <map> Library