public bool Remove(T itemToRemove)
{
DoubelLinkedListItem <T> chosenOne = Find(itemToRemove, out bool isStartItem);
if (itemToRemove == null)
{
return(false);
}
//1. Fall: Erstes Element wird entfernt
if (isStartItem)
{
_firstItem.nextItem.ItemBefore = null;
_firstItem = _firstItem.nextItem;
return(true);
}
else //2.Fall irgendwo in der Mitte
{
if (chosenOne.nextItem == null) //3.Fall: das Element am Ende wird entfernt
{
chosenOne.ItemBefore.nextItem = null;
}
else
{
chosenOne.ItemBefore.nextItem = chosenOne.nextItem;
chosenOne.nextItem.ItemBefore = chosenOne.ItemBefore;
return(true);
}
}
return(false);
}
public DoubelLinkedListItem <T> FindRekursiv(T itemToFind, DoubelLinkedListItem <T> actItem = null)
{
if (itemToFind == null) //Parameter überpüfen
{
return(null);
}
if (this._firstItem == null) //DLL leer ?
{
return(null);
}
if (actItem == null) //actitem == null, bedeutet dass die find am Beginn der DLL starten soll
{
actItem = this._firstItem;
}
else //nach mehrmaligen aufruf, Zeiger aufs nächste Item setzen
{
actItem = actItem.nextItem;
}
if (actItem == null)//Ende der Liste ist erreicht , sonst wird auf actItem.nextItem gesetz
{
return(null);
}
else if (actItem.Item.Equals(itemToFind)) // gesuchtes Item gefunden
{
return(actItem);
}
else // Methode wird nocheinmal aufgerufen, mit actItem
{
return(FindRekursiv(itemToFind, actItem));
}
}
public DoubelLinkedListItem <T> Find(T itemToFind, out bool isStartItem)
{
isStartItem = false;
if (itemToFind == null)
{
return(null);
}
if (_firstItem == null)
{
return(null);
}
//1. Fall Object ist erster Eintrag
if (this._firstItem.Item.Equals(itemToFind))
{
isStartItem = true;
return(_firstItem);
}
//2. Fall: irgendwo
DoubelLinkedListItem <T> actItem = _firstItem;
while (actItem != null)
{
if (actItem.Item.Equals(itemToFind))
{
return(actItem);
}
actItem = actItem.nextItem;
}
return(null);
}
public bool AddItemAfterItem(T itemToAdd, T targetItem)
{
if ((itemToAdd == null) || (targetItem == null))
{
return(false);
}
bool isStartItem;
DoubelLinkedListItem <T> chosenOne = Find(targetItem, out isStartItem);
DoubelLinkedListItem <T> toAddItem = new DoubelLinkedListItem <T>(itemToAdd, null, null);
DoubelLinkedListItem <T> actItem = _firstItem;
while (actItem != null)
{
if (chosenOne.Item.Equals(actItem.Item))
{
toAddItem.ItemBefore = actItem;
toAddItem.nextItem = actItem.nextItem;
actItem.nextItem = toAddItem;
actItem.nextItem.ItemBefore = toAddItem;
return(true);
}
actItem = actItem.nextItem;
}
return(false);
}
public bool Change(T itemToChange, T newItem)
{
if (itemToChange == null)
{
return(false);
}
bool isStartItem;
DoubelLinkedListItem <T> chosenOne = Find(itemToChange, out isStartItem);
DoubelLinkedListItem <T> actItem = this._firstItem;
while (actItem != null)
{
if (chosenOne.Item.Equals(actItem.Item))
{
actItem.Item = newItem;
}
actItem = actItem.nextItem;
}
return(false);
}
public override string ToString()
{
string s = "";
if (this._firstItem != null)
{
DoubelLinkedListItem <T> actItem = this._firstItem;
while (actItem != null)
{
s += actItem.Item.ToString() + "\n";
actItem = actItem.nextItem;
}
}
if (s == "")
{
return(" no Item");
}
return(s);
}
public bool Add(T itemToAdd)
{
if (itemToAdd == null)
{
return(false);
}
//1. Fall: das erste Item in der Liste
if (_firstItem == null)
{
_firstItem = new DoubelLinkedListItem <T>(itemToAdd, null, null);
_lastItem = _firstItem;
return(true);
}
else
{
DoubelLinkedListItem <T> toAdd = new DoubelLinkedListItem <T>(itemToAdd, _lastItem, null);
this._lastItem.nextItem = toAdd;
this._lastItem = toAdd;
return(true);
}
}
public DoubelLinkedListItem(T p, DoubelLinkedListItem <T> ItemBefore, DoubelLinkedListItem <T> nextItem)
{
this.Item = p;
this.ItemBefore = ItemBefore;
this.nextItem = nextItem;
}
public DoubleLinkedList(DoubleLinkedList <T> dll)
{
this._firstItem = dll._firstItem;
this._lastItem = dll._lastItem;
}
public DoubleLinkedList(T item)
{
this._firstItem = new DoubelLinkedListItem <T>(item, null, null);
this._lastItem = _firstItem;
}
public DoubleLinkedList()
{
this._firstItem = null;
this._lastItem = null;
}
