map::rbegin
Returns an iterator addressing the first element in a reversed map.
const_reverse_iterator rbegin( ) const;
reverse_iterator rbegin( );
Return Value
A reverse bidirectional iterator addressing the first element in a reversed map or addressing what had been the last element in the unreversed map.
Remarks
rbegin is used with a reversed map just as begin is used with a map.
If the return value of rbegin is assigned to a const_reverse_iterator, then the map object cannot be modified. If the return value of rbegin is assigned to a reverse_iterator, then the map object can be modified.
rbegin can be used to iterate through a map backwards.
Example
// map_rbegin.cpp
// compile with: /EHsc
#include <map>
#include <iostream>
int main( )
{
using namespace std;
map <int, int> m1;
map <int, int> :: iterator m1_Iter;
map <int, int> :: reverse_iterator m1_rIter;
map <int, int> :: const_reverse_iterator m1_crIter;
typedef pair <int, int> Int_Pair;
m1.insert ( Int_Pair ( 1, 10 ) );
m1.insert ( Int_Pair ( 2, 20 ) );
m1.insert ( Int_Pair ( 3, 30 ) );
m1_rIter = m1.rbegin( );
cout << "The first element of the reversed map m1 is "
<< m1_rIter -> first << "." << endl;
// begin can be used to start an iteration
// through a map in a forward order
cout << "The map is: ";
for ( m1_Iter = m1.begin( ) ; m1_Iter != m1.end( ); m1_Iter++)
cout << m1_Iter -> first << " ";
cout << "." << endl;
// rbegin can be used to start an iteration
// through a map in a reverse order
cout << "The reversed map is: ";
for ( m1_rIter = m1.rbegin( ) ; m1_rIter != m1.rend( ); m1_rIter++)
cout << m1_rIter -> first << " ";
cout << "." << endl;
// A map element can be erased by dereferencing to its key
m1_rIter = m1.rbegin( );
m1.erase ( m1_rIter -> first );
m1_rIter = m1.rbegin( );
cout << "After the erasure, the first element "
<< "in the reversed map is "
<< m1_rIter -> first << "." << endl;
}
The first element of the reversed map m1 is 3. The map is: 1 2 3 . The reversed map is: 3 2 1 . After the erasure, the first element in the reversed map is 2.
Requirements
Header: <map>
Namespace: std