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multimap sample

Posted on 2002-07-10
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Last Modified: 2011-09-20
hi,
i need a simple sample that show basic usage of stl multimap.
insert, delete, move through members of specific key, etc.

thank u in advance
efratk :-)
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Question by:efratk
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6 Comments
 
LVL 22

Expert Comment

by:ambience
ID: 7145366
//////// Demonstrates delete and insert

#include <map>
#include <iostream>

int main( )
{
   using namespace std;
   multimap <int, int> m1, m2, m3;
   multimap <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 multimap ms1 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 multimap 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
   m3.insert( Int_Pair ( 2, 5 ) );
   n = m3.erase( 2 );

   cout << "After the element with a key of 2 is deleted,\n"
        << "the multimap 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 multimap m3 is:" ;
   for ( pIter = m3.begin( ) ; pIter != m3.end( ) ; pIter++ )
      cout << " " << pIter -> second;
   cout << "." << endl;
}
0
 
LVL 22

Expert Comment

by:ambience
ID: 7145369
/// Demostrates find

#include <map>
#include <iostream>

int main( )
{
   using namespace std;
   multimap <int, int> m1;
   multimap <int, int> :: const_iterator m1_AcIter, m1_RcIter;
   typedef pair <int, int> Int_Pair;

   m1.insert ( Int_Pair ( 1, 10 ) );
   m1.insert ( Int_Pair ( 2, 20 ) );
   m1.insert ( Int_Pair ( 3, 20 ) );
   m1.insert ( Int_Pair ( 3, 30 ) );

   m1_RcIter = m1.find( 2 );
   cout << "The element of multimap m1 with a key of 2 is: "
        << m1_RcIter -> second << "." << endl;

   m1_RcIter = m1.find( 3 );
   cout << "The first element of multimap m1 with a key of 3 is: "
        << m1_RcIter -> second << "." << endl;

   // If no match is found for the key, end( ) is returned
   m1_RcIter = m1.find( 4 );

   if ( m1_RcIter == m1.end( ) )
      cout << "The multimap m1 doesn't have an element "
           << "with a key of 4." << endl;
   else
      cout << "The element of multimap m1 with a key of 4 is: "
           << m1_RcIter -> second << "." << endl;

   // The element at a specific location in the multimap can be
   // found using a dereferenced iterator addressing the location
   m1_AcIter = m1.end( );
   m1_AcIter--;
   m1_RcIter = m1.find( m1_AcIter -> first );
   cout << "The first element of m1 with a key matching"
        << endl << "that of the last element is: "
        << m1_RcIter -> second << "." << endl;

   // Note that the first element with a key equal to
   // the key of the last element is not the last element
   if ( m1_RcIter == --m1.end( ) )
      cout << "This is the last element of multimap m1."
           << endl;
   else
      cout << "This is not the last element of multimap m1."
           << endl;
}
0
 
LVL 22

Expert Comment

by:ambience
ID: 7145377
// demostrates insert and traversals

#include <map>
#include <iostream>

int main( )
{
   using namespace std;
   multimap <int, int>::iterator m1_pIter, m2_pIter;

   multimap <int, int> m1, m2;
   typedef pair <int, int> Int_Pair;

   m1.insert ( Int_Pair ( 1, 10 ) );
   m1.insert ( Int_Pair ( 2, 20 ) );
   m1.insert ( Int_Pair ( 3, 30 ) );

   cout << "The original key values of m1 =";
   for ( m1_pIter = m1.begin( ); m1_pIter != m1.end( ); m1_pIter++ )
      cout << " " << m1_pIter -> first;
   cout << "." << endl;

   cout << "The original mapped values of m1 =";
   for ( m1_pIter = m1.begin( ); m1_pIter != m1.end( ); m1_pIter++ )
      cout << " " << m1_pIter -> second;
   cout << "." << endl;

   m1.insert ( Int_Pair ( 1, 10 ) );

   // The hint version of insert
   m1.insert( --m1.end( ), Int_Pair ( 4, 40 )  );

   cout << "After the insertions, the key values of m1 =";
   for ( m1_pIter = m1.begin( ); m1_pIter != m1.end( ); m1_pIter++ )
      cout << " " << m1_pIter -> first;
   cout << "," << endl;

   cout << " and the mapped values of m1 =";
   for ( m1_pIter = m1.begin( ); m1_pIter != m1.end( ); m1_pIter++ )
      cout << " " << m1_pIter -> second;
   cout << "." << endl;

   m2.insert ( Int_Pair ( 10, 100 ) );

   // The templatized version inserting a range
   m2.insert( ++m1.begin( ), --m1.end( ) );

   cout << "After the insertions, the key values of m2 =";
   for ( m2_pIter = m2.begin( ); m2_pIter != m2.end( ); m2_pIter++ )
      cout << " " << m2_pIter -> first;
   cout << "," << endl;

   cout << " and the mapped values of m2 =";
   for ( m2_pIter = m2.begin( ); m2_pIter != m2.end( ); m2_pIter++ )
      cout << " " << m2_pIter -> second;
   cout << "." << endl;
}
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Author Comment

by:efratk
ID: 7145790
hi ambience,

first, i want to thank u a lot for the detailed answer.
but, i would like to know also how to move through all the members with a specific key.

thanks again
efratk
0
 
LVL 22

Accepted Solution

by:
ambience earned 1600 total points
ID: 7145835
int main( )
{
   typedef multimap <int, int, less<int> > IntMMap;
   typedef IntMMap::iterator IntMMapIter;
   typedef pair <int, int> Int_Pair;

   IntMMap m1;
   IntMMapIter m1_RcIter;

   m1.insert ( Int_Pair ( 1, 10 ) );
   m1.insert ( Int_Pair ( 2, 20 ) );
   m1.insert ( Int_Pair ( 2, 30 ) );
   m1.insert ( Int_Pair ( 3, 30 ) );
   m1.insert ( Int_Pair ( 2, 40 ) );
   m1.insert ( Int_Pair ( 2, 50 ) );

   pair <IntMMapIter, IntMMapIter> p1, p2;
   p1 = m1.equal_range( 2 );

   IntMMapIter i = p1.first;
   for(; i != p1.second; ++i)
   {
        cout << "key of 2 has value: " << i-> second << "." << endl;

   }
   return 0;
}
0
 

Author Comment

by:efratk
ID: 7145873
ambience,
thank u very much
efrat
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