public void Add(object value)
{
LinkedItem addedItem = new LinkedItem { Value = value, Next = null };
if (_last == null)
{
_last = addedItem;
_last.Previous = null;
//keep track of that very first item to make it easy to traverse the list
_start = _last;
return;
}
_last.Next = addedItem;
addedItem.Previous = _last;
_last = addedItem;
}
//public override string ToString()
//{
// StringBuilder strBuilder = new StringBuilder();
// LinkedItem currentItem = _start;
// while (currentItem != null )
// {
// if (strBuilder.Length > 0)
// strBuilder.Append(", ");
// strBuilder.Append(currentItem.ToString());
// currentItem = currentItem.Next;
// }
// return strBuilder.ToString();
//}
private void insertBefore(LinkedItem targetItem, LinkedItem itemTobeAdded)
{
if (targetItem == null)
return;
LinkedItem previousItem = targetItem.Previous;
previousItem.Next = itemTobeAdded;
itemTobeAdded.Next = targetItem;
targetItem.Previous = itemTobeAdded;
}
public void Reverse()
{
LinkedItem currentItem = _last;
_last = _start;
_start = currentItem;
while (currentItem != null)
{
LinkedItem previousItem = currentItem.Previous;
currentItem.Previous = currentItem.Next;
currentItem.Next = previousItem;
currentItem = previousItem;
}
}
public object Pop()
{
if (_last == null)
return null;
object poppedValue = _last.Value;
_last = _last.Previous;
_last.Next = null;
return poppedValue;
}
public void ConstrainedReverse()
{
//if our list was truly a linked list not a double linked list
LinkedItem currentItem = _start;
LinkedItem previousItem = null;
_last = _start;
while (currentItem != null)
{
_start = currentItem;
var nextItem = currentItem.Next;
currentItem.Next = previousItem;
previousItem = currentItem;
currentItem = nextItem;
}
}
public void AddAt(object value, int index)
{
LinkedItem currentItem = getAt(index);
LinkedItem itemToAdd = new LinkedItem { Value = value };
if (currentItem == null)
throw new ArgumentException("Index provided is invalid: list does not have that many items in it");
insertBefore(currentItem, itemToAdd);
}
