Re: Algorithm for performing a rollup

Chris <spam_me_not@goaway.com> wrote:


Arne gave the hint with the Map idea. Here's a version of how I would attempt
such a thing:

First off, let's put the Strings into a List so we can go all Collections.

public class Foo
{

   public static void main( String [] args )
   {
     List< String > starters =
         Arrays.asList( "A", "A", "A", "B", "B", "C", "D", "D" );

     Map< String, Integer > kounts = new HashMap();
     for( String key : starters )
     {
       Integer k = kounts.get( key );
       if ( k == null )
       {
         kounts.put( key, 1 );
       }
       else
       {
         kounts.put( key, k + 1 );
       }
     }

     List< String > outters = new ArrayList< String >();
     outters.addAll( kounts.keySet() );
     Collections.sort( outters );

     for ( String key : outters )
     {
       System.out.println( "\""+ key + "\", "+ kounts.get( key ));
     }
   }
}

-- Lew