chapter10-9.cpp

C++STL程序员开发指南

//文件名:CHAPTER10-9.cpp
#include <map>
#include <iostream>
#if _MSC_VER > 1020   // if VC++ version is > 4.2
   using namespace std;  // std c++ libs implemented in std
#endif
void main( )
{
   map <int, int> m1;
   int i;
   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.rend( );
   m1_rIter--;
   cout << "The last 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.rend( );
   m1.erase ( m1_rIter -> first );
   m1_rIter = m1.rend( );
   m1_rIter--;
   cout << "After the erasure, the last element "<< "in the reversed map is "
        << m1_rIter -> first << "." << endl;
}