//文件名:CHAPTER9-25.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> :: const_iterator s1_AcIter, s1_RcIter;
   s1.insert( 10 );
   s1.insert( 20 );
   s1.insert( 30 );
   s1_RcIter = s1.find( 20 );
   cout << "The element of set s1 with a key of 20 is: "<< *s1_RcIter << "." << endl;
   s1_RcIter = s1.find( 40 );
   // If no match is found for the key, end( ) is returned
   if ( s1_RcIter == s1.end( ) )
      cout << "The set s1 doesn't have an element "<< "with a key of 40." << endl;
   else
      cout << "The element of set s1 with a key of 40 is: "<< *s1_RcIter << "." << endl;
   // The element at a specific location in the set can be found 
   // by using a dereferenced iterator addressing the location
   s1_AcIter = s1.end( );
   s1_AcIter--;
   s1_RcIter = s1.find( *s1_AcIter );
   cout << "The element of s1 with a key matching "<< "that of the last element is: "
        << *s1_RcIter << "." << endl;
}