public MyLinkedListItem <T> Modify(MyLinkedListItem <T> newItem)
{
MyLinkedListItem <T> temp = _next;
_next = newItem;
return(_next);
}
/// <summary>
/// FindItemDescending - Finds the the nth number item from the start of the list
///
/// </summary>
/// <param name="nth"> This parameter is assumed to be index 1 instead of index 0 based.</param>
/// <returns></returns>
private MyLinkedListItem <T> FindItemAscending(ulong nth)
{
if (_start == null)
{
return(null);
}
//No need to search the list if item is index 1 since that is the start item.
if (nth == 1)
{
return(_start);
}
MyLinkedListItem <T> temp = _start;
ulong index = 0;
while (temp != null)
{
//Once item index found return that item and terminate search.
if (++index == nth)
{
return(temp);
}
temp = temp.Next;
}
//If itemNumber index is not reached then there were not enough items in the list.
return(null);
}
/// <summary>
/// FindItemDescending - Finds the the nth number item from the end of the list
/// The algorithm requires at least one full pass on the entire list so that we can find the end of the list
/// Because we can only traverse the list once, we have to save each reference for each item access into
/// a revolving collection stored in arrayOfReference which is the size of the item trying to be found
///
/// </summary>
/// <param name="nth"> This parameter is assumed to be index 1 instead of index 0 based.</param>
/// <returns></returns>
private MyLinkedListItem <T> FindItemDescending(ulong nth)
{
MyLinkedListItem <T>[] arrayOfReferences = new MyLinkedListItem <T> [nth];
MyLinkedListItem <T> temp = _start;
MyLinkedListItem <T> retItem = null;
//If there is a null linked list then return null;
if (_start == null || nth == 0)
{
return(null);
}
ulong index = 0;
while (temp.Next != null)
{
//Continue writing items into array. If we exceed nth then
//the mod operation will begin overwriting entries at the beginning of
//the array.
arrayOfReferences[index++ % nth] = temp;
temp = temp.Next;
}
if (index >= nth)
{
retItem = arrayOfReferences[index % nth];
}
return(retItem);
}
public void Push(T itemVal)
{
if (_start == null)
{
_start = new MyLinkedListItem <T>(itemVal);
_end = _start;
}
else
{
_end = _end.Add(itemVal);
}
}
public MyLinkedListItem <T> FindItem(ulong itemNumber, MyLinkListSearchDirection direction)
{
MyLinkedListItem <T> retItem = null;
switch (direction)
{
case MyLinkListSearchDirection.Ascending:
retItem = FindItemAscending(itemNumber);
break;
case MyLinkListSearchDirection.Descending:
retItem = FindItemDescending(itemNumber);
break;
}
return(retItem);
}
public void Clear()
{
if (_start == null)
{
return;
}
MyLinkedListItem <T> current = _start;
MyLinkedListItem <T> next = _start.Next;
while (next != null)
{
next = current.Next;
current.Unlink();
}
_start = null;
}
private void btnSearch_Click(object sender, EventArgs e)
{
ulong itemNumber = 0;
if (!ulong.TryParse(txtItemNumber.Text, out itemNumber))
{
MessageBox.Show("Please enter a valid non-negative number into the Item Number field.", "Data Entry Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
txtItemNumber.Focus();
txtItemNumber.SelectAll();
return;
}
MyLinkListSearchDirection searchType = (cmbSearchType.Text == "ASC") ? MyLinkListSearchDirection.Ascending : MyLinkListSearchDirection.Descending;
string searchDataResult = "Unable to find entry. Item Number is out of range.";
if (bIntegerOrString)
{
if (IntegerLinkedList.IsEmpty)
{
MessageBox.Show("Please load a file with integer data.", "Integer Data Empty", MessageBoxButtons.OK, MessageBoxIcon.Information);
return;
}
MyLinkedListItem <long> item = IntegerLinkedList.FindItem(itemNumber, searchType);
if (item != null)
{
searchDataResult = string.Format("Integer data found at position {0} from {1} of linked list.{2}Value: {3}", itemNumber,
(searchType == MyLinkListSearchDirection.Ascending) ? "front" : "back", Environment.NewLine, item.Value);
}
}
else
{
if (StringLinkedList.IsEmpty)
{
MessageBox.Show("Please load a file with string data.", "String Data Empty", MessageBoxButtons.OK, MessageBoxIcon.Information);
return;
}
MyLinkedListItem <string> item = StringLinkedList.FindItem(itemNumber, searchType);
if (item != null)
{
searchDataResult = string.Format("String data found at position {0} from {1} of linked list.{2}Value: {3}", itemNumber,
(searchType == MyLinkListSearchDirection.Ascending) ? "front" : "back", Environment.NewLine, item.Value);
}
}
txtFoundData.Text = searchDataResult;
}
public void Unlink()
{
_next = null;
}
public void Add(MyLinkedListItem <T> item)
{
_next = item;
}
public MyLinkedListItem <T> Add(T item)
{
this._next = new MyLinkedListItem <T>(item);
return(this._next);
}
public MyLinkedListItem(T item)
{
Value = item;
_next = null;
}
