hash_map::rbegin
Note
This API is obsolete. The alternative is unordered_map Class.
Returns an iterator addressing the first element in a reversed hash_map.
const_reverse_iterator rbegin( ) const;
reverse_iterator rbegin( );
Return Value
A reverse bidirectional iterator addressing the first element in a reversed hash_map or addressing what had been the last element in the unreversed hash_map.
Remarks
rbegin is used with a reversed hash_map just as begin is used with a hash_map.
If the return value of rbegin is assigned to a const_reverse_iterator, then the hash_map object cannot be modified. If the return value of rbegin is assigned to a reverse_iterator, then the hash_map object can be modified.
rbegin can be used to iterate through a hash_map backwards.
In Visual C++ .NET 2003, members of the <hash_map> and <hash_set> header files are no longer in the std namespace, but rather have been moved into the stdext namespace. See The stdext Namespace for more information.
Example
// hash_map_rbegin.cpp
// compile with: /EHsc
#include <hash_map>
#include <iostream>
int main( )
{
using namespace std;
using namespace stdext;
hash_map <int, int> hm1;
hash_map <int, int> :: iterator hm1_Iter;
hash_map <int, int> :: reverse_iterator hm1_rIter;
hash_map <int, int> :: const_reverse_iterator hm1_crIter;
typedef pair <int, int> Int_Pair;
hm1.insert ( Int_Pair ( 1, 10 ) );
hm1.insert ( Int_Pair ( 2, 20 ) );
hm1.insert ( Int_Pair ( 3, 30 ) );
hm1_rIter = hm1.rbegin( );
cout << "The first element of the reversed hash_map hm1 is "
<< hm1_rIter -> first << "." << endl;
// begin can be used to start an iteration
// through a hash_map in a forward order
cout << "The hash_map is: ";
for ( hm1_Iter = hm1.begin( ) ; hm1_Iter != hm1.end( ); hm1_Iter++)
cout << hm1_Iter -> first << " ";
cout << "." << endl;
// rbegin can be used to start an iteration
// through a hash_map in a reverse order
cout << "The reversed hash_map is: ";
for ( hm1_rIter = hm1.rbegin( ) ; hm1_rIter != hm1.rend( ); hm1_rIter++)
cout << hm1_rIter -> first << " ";
cout << "." << endl;
// A hash_map element can be erased by dereferencing to its key
hm1_rIter = hm1.rbegin( );
hm1.erase ( hm1_rIter -> first );
hm1_rIter = hm1.rbegin( );
cout << "After the erasure, the first element "
<< "in the reversed hash_map is "
<< hm1_rIter -> first << "." << endl;
}
The first element of the reversed hash_map hm1 is 3. The hash_map is: 1 2 3 . The reversed hash_map is: 3 2 1 . After the erasure, the first element in the reversed hash_map is 2.
Requirements
Header: <hash_map>
Namespace: stdext