/**
* Sorts the host list in ascending order.  Assumes host list contains Integer objects.
<pre>
Selection sort algorithm:
Case list is empty: do nothing
Case list is not empty:
    Find the minimum element of the list.
    Move it to the front of the list.
    Recur on the rest of the list.
</pre>
* @author Dung X. Nguyen - Copyright 1999 - All rights reserved.
*/
public class SelectSort implements IAlgo
{
	public final static SelectSort Singleton = new SelectSort ();

	private SelectSort()
	{
	}

	/**
	 * @param host 
	 * @param input 
	 * @return 
	 */
	public Object nullCase(QFList host, Object input)
	{
		return null;
	}

	/**
	 * @param host 
	 * @param input 
	 * @return 
	 */
	public Object nonNullCase(QFList host, Object input)
	{
      host.insertFront(host.execute(RemMin.Singleton,null));
		return host.getRest().execute(this, null);
	}

	public static void main(String[] args)
	{
      QFList l1 = new QFList ();
      l1.insertFront (new Integer (-9));
      l1.insertFront (new Integer (15));
      l1.insertFront (new Integer (263));
      l1.insertFront (new Integer (-72));
      System.out.println ("l1: " + l1);
      System.out.println ("Sorting l1...");
      l1.execute(SelectSort.Singleton, null);
      System.out.println ("l1: " + l1);
      try
      {
         System.out.println ("Press Enter to quit...");
         System.in.read ();
      }
      catch (Exception e)
      {
      }
   }
}