C++ Map Library - rend() Function

Description

The C++ function std::map::rend() returns a reverse iterator which points to the reverse end of the map i.e. beginning of the map.

Declaration

Following is the declaration for std::map::rend() function form std::map header.

C++98

reverse_iterator rend();
const_reverse_iterator rend() const;

C++11

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

Parameters

None

Return value

If object is constant qualified then method returns constant reverse iterator otherwise non-constant reverse iterator.

Exceptions

This member function never throws exception.

Time complexity

Constant i.e. O(1)

Example

The following example shows the usage of std::map::rend() function.

#include <iostream>
#include <map>

using namespace std;

int main(void) {
   /* Initializer_list constructor */
   map<char, int> m = {
            {'a', 1},
            {'b', 2},
            {'c', 3},
            {'d', 4},
            {'e', 5},
            };

   cout << "Map contains following elements in reverse order" << endl;

   for (auto it = m.rbegin(); it != m.rend(); ++it)
      cout << it->first << " = " << it->second << endl;

   return 0;
}

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

Map contains following elements in reverse order
e = 5
d = 4
c = 3
b = 2
a = 1