C++ Map Library - rbegin() Function


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Description

The C++ function std::map::rbegin() returns a reverse iterator which points to the last element of the map.

Reverse iterator iterates in reverse order that is why incrementing them moves towards beginning of map.

Declaration

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

C++98

reverse_iterator rbegin();
const_reverse_iterator rbegin() const;

C++11

reverse_iterator rbegin() noexcept;
const_reverse_iterator rbegin() 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::rbegin() 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
map.htm
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