Algorithms

public class HybridList: System.Collections.CollectionBase
{
   Hashtable _indicesTable = new Hashtable();

   public int IndexOf(object key)
   {
      if(_indicesTable.ContainsKey(key))
         return (int)_indicesTable[key];
      else
         return -1;
   }
   public int Add(object key, object val)
   {
      int index = List.Add(new DictionaryEntry(key, val));
      _indicesTable[key] = index;
      return index;
   }
   public void Remove(object key)
   {
      if(_indicesTable.ContainsKey(key))
      {
         List.RemoveAt((int)_indicesTable[key]);
         _indicesTable.Remove(key);
         int i = 0;
         foreach(DictionaryEntry entry in List)
         _indicesTable[entry.Key] = i++;
      }
   }
   public DictionaryEntry this[int index]
   {
      get { return ((DictionaryEntry)List[index]); }
   }
   public object this[object key]
   {
      get
      {
         if(_indicesTable.ContainsKey(key))
            return ((DictionaryEntry)List[(int)_indicesTable[key]]).Value;
         else
            return null;
      }
   }
   public ICollection AllKeys
   {
      get { return _indicesTable.Keys; }
   }
	
   protected override void OnClear()
   {
      base.OnClear();
      _indicesTable.Clear();
   }
}

Ray Kinsella wrote:

I occasionally end up with variations which significantly throw out the average, sometimes unfairly.

<br />
for (a=1;a<=12;a++)<br />
{<br />
  printf(2^(a-1));<br />
}<br />

cp9876 wrote:

Why - has it better performance?

for (i=0 ; i < iMax-1; i++)
{
  int temp = a[i];
  if (temp > 51) continue;

  for ( j=i+1; j < iMax; j++)
  {
    if (temp + a[j] == 51)
    {
      // do whatever you need...
    }
  }
}