chapter10-19.cpp

C++STL程序员开发指南

//文件名:CHAPTER10-19.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, m2, m3;
   map <int, int> :: iterator pIter, Iter1, Iter2;
   int i, n;
   typedef pair <int, int> Int_Pair;
   for ( i = 1 ; i < 5 ; i++ )
   {
      m1.insert ( Int_Pair ( i, i ) );
      m2.insert ( Int_Pair ( i, i*i ) );
      m3.insert ( Int_Pair ( i, i-1 ) );
   }
   // The 1st member function removes an element at a given position
   Iter1 = ++m1.begin( );
   m1.erase( Iter1 );
   cout << "After the 2nd element is deleted, the map m1 is:" ;
   for ( pIter = m1.begin( ) ; pIter != m1.end( ) ; pIter++ )
      cout << " " << pIter -> second;
   cout << "." << endl;
   // The 2nd member function removes elements in the range [_First, _Last)
   Iter1 = ++m2.begin( );
   Iter2 = --m2.end( );
   m2.erase( Iter1, Iter2 );
   cout << "After the middle two elements are deleted,"<< " the map m2 is:" ;
   for ( pIter = m2.begin( ) ; pIter != m2.end( ) ; pIter++ )
      cout << " " << pIter -> second;
   cout << "." << endl;
   // The 3rd member function removes elements with a given _Key
   n = m3.erase( 2 );
   cout << "After the element with a key of 2 is deleted,\n"<< "the map m3 is:" ;
   for ( pIter = m3.begin( ) ; pIter != m3.end( ) ; pIter++ )
      cout << " " << pIter -> second;
   cout << "." << endl;
   // The 3rd member function returns the number of elements removed
   cout << "The number of elements removed from m3 is: "<< n << "." << endl;
   // The dereferenced iterator can also be used to specify a key
   Iter1 = ++m3.begin( );
   m3.erase( Iter1 );
   cout << "After another element with a key equal to that"<< endl;
   cout  << "of the 2nd element is deleted, "<< "the map m3 is:" ;
   for ( pIter = m3.begin( ) ; pIter != m3.end( ) ; pIter++ )
      cout << " " << pIter -> second;
   cout << "." << endl;
}