} // end method RemoveFromFront
// remove last node from List
public object RemoveFromBack()
{
if (IsEmpty())
{
throw new EmptyListException();
}
object removeItem = lastNode.Data; // retrieve data
// reset firstNode and lastNode references
if (firstNode == lastNode)
{
firstNode = lastNode = null;
}
else
{
TwoWayListNode current = firstNode;
// loop while current.Next is not lastNode
while (current.Next != lastNode)
{
current = current.Next; // move to next node
}
// current is new lastNode
lastNode = current;
current.Next = null;
} // end else
lenght--;
return(removeItem); // return removed data
} // end method RemoveFromBack
} // end method InsertAtFront
// Insert object at end of List. If List is empty,
// firstNode and lastNode will refer to same object.
// Otherwise, lastNode's Next property refers to new node.
public void InsertAtBack(object insertItem)
{
if (IsEmpty())
{
firstNode = lastNode = new TwoWayListNode(insertItem);
}
else
{
lastNode = lastNode.Next = new TwoWayListNode(insertItem, null, lastNode);
}
lenght++;//lenght increasment after adding an element.
} // end method InsertAtBack
} // end method IsEmpty
// output List contents
public void Display()
{
if (IsEmpty())
{
Console.WriteLine("Empty ");
} // end if
else
{
Console.Write("The list is: ");
TwoWayListNode current = firstNode;
// output current node data while not at end of list
while (current != null)
{
Console.Write(current.Data + " ");
current = current.Next;
} // end while
Console.WriteLine("\n");
} // end else
} // end method Display
//indexer implementation to use list like array.
public object this[int index]
{
set
{
if (index >= 0 && index <= lenght)
{
TwoWayListNode current = firstNode;
for (int i = 0; i < index; i++)
{
current = current.Next;
}
current.Data = value;
}
else
{
throw new IndexOutOfRangeException();
}
}
get
{
if (index >= 0 && index <= lenght)
{
TwoWayListNode current = firstNode;
for (int i = 0; i < index; i++)
{
current = current.Next;
}
return(current.Data);
}
else
{
throw new IndexOutOfRangeException();
}
}
}
} // end method InsertAtBack
// remove first node from List
public object RemoveFromFront()
{
if (IsEmpty())
{
throw new EmptyListException();
}
object removeItem = firstNode.Data; // retrieve data
// reset firstNode and lastNode references
if (firstNode == lastNode)
{
firstNode = lastNode = null;
}
else
{
firstNode = firstNode.Next;
firstNode.Back = null;
}
lenght--;
return(removeItem); // return removed data
} // end method RemoveFromFront
// construct empty List
public TwoWayLinkedList()
{
lenght = 0;//At first lenght value is 0.
firstNode = lastNode = null;
} // end default constructor
} // end default constructor
// constructor to create TwoWayListNode that refers to dataValue
// and refers to next TwoWayListNode in List
public TwoWayListNode(object dataValue, TwoWayListNode nextNode, TwoWayListNode backNode)
{
Data = dataValue;
Next = nextNode;
Back = backNode;
} // end constructor
