//文件名:CHAPTER9-7.cpp
#include <set>
#include <iostream>
#if _MSC_VER > 1020   // if VC++ version is > 4.2
   using namespace std;  // std c++ libs implemented in std
#endif
int main( )
{
   set <int> s1;
   set <int>::iterator s1_Iter;
   set <int>::reverse_iterator s1_rIter;
   s1.insert( 10 );
   s1.insert( 20 );
   s1.insert( 30 );
   s1_rIter = s1.rbegin( );
   cout << "The first element in the reversed set is "
        << *s1_rIter << "." << endl;
   // begin can be used to start an iteration throught a set in a forward order
   cout << "The set is:";
   for ( s1_Iter = s1.begin( ) ; s1_Iter != s1.end( ); s1_Iter++ )
      cout << " " << *s1_Iter;
   cout << endl;
   // rbegin can be used to start an iteration throught a set in a reverse order
   cout << "The reversed set is:";
   for ( s1_rIter = s1.rbegin( ) ; s1_rIter != s1.rend( ); s1_rIter++ )
      cout << " " << *s1_rIter;
   cout << endl;
   // A set element can be erased by dereferencing to its key 
   s1_rIter = s1.rbegin( );
   s1.erase ( *s1_rIter );
   s1_rIter = s1.rbegin( );
   cout << "After the erasure, the first element "
        << "in the reversed set is "<< *s1_rIter << "." << endl;
}