public static bool Delete <T>(this Skiplist <T> skiplist, T key)
{
if (skiplist.Head == null)
{
return(false);
}
if (skiplist.Head.Down == null && skiplist.AreEqual(skiplist.Head.Key, key))
{
return(TryRemoveCurrentHead(skiplist, key));
}
var keyFound =
skiplist.Find(
key: key,
pathAction: node => HandlePathToDeletionPoint(node, key, skiplist.MinimumGapSize, skiplist.AreEqual),
origin: skiplist.Head.Down);
if (skiplist.Head.Down.LengthOfList() <= 1)
{
skiplist.Head = skiplist.Head.Down;
skiplist.Head.Up = null;
}
return(keyFound);
}
public static bool Find <T>(
this Skiplist <T> skiplist,
T key,
INode <T> origin = null,
Action <INode <T> > pathAction = null)
{
var nodeOfKey = skiplist.FetchNode(key, origin, pathAction);
return(skiplist.AreEqual(nodeOfKey.Key, key));
}
private static void InserterAction <T>(T key, Skiplist <T> skiplist, INode <T> pathNode)
{
if (pathNode.Down == null)
{
InsertKeyAfterNode(key, pathNode, skiplist.NodeFactory);
}
else if (pathNode.SizeOfGap() >= skiplist.MaximumGapSize)
{
SplitGap(pathNode, skiplist.NodeFactory);
}
}
private static bool TryRemoveCurrentHead <T>(Skiplist <T> skiplist, T key)
{
if (skiplist.Head.Right == skiplist.Head && skiplist.AreEqual(skiplist.Head.Key, key))
{
skiplist.Head = null;
return(true);
}
else
{
return(false);
}
}
private static string CreateFormatFor <T>(Skiplist <T> skiplist)
{
var bottomNodes = skiplist.Head.Bottom().EnumerateRight().ToList();
var numberOfColumns = bottomNodes.Count();
var columnWidth = bottomNodes.Max(node => node.Key.ToString().Length) + 1;
var nodeFormat = Enumerable.Range(0, numberOfColumns).Select(i => "{" + i + ", -" + (columnWidth) + "}").ToArray();
var levelFormat = string.Concat(nodeFormat);
return(levelFormat);
}
public static string StringOf <T>(Skiplist <T> skiplist)
{
if (skiplist.Head == null)
{
return("Empty");
}
else
{
var format = CreateFormatFor(skiplist);
var levels = skiplist.Head.EnumerateDown();
var levelStrings = levels.Select(level => FormatLevel(level, format) + "\n").ToArray();
return(String.Concat(levelStrings));
}
}
public static void Insert <T>(this Skiplist <T> skiplist, T key)
{
if (skiplist.Head == null)
{
skiplist.Head = skiplist.NodeFactory(key);
skiplist.Head.ConnectTo(skiplist.Head);
return;
}
skiplist.Find(key, pathAction: node => InserterAction(key, skiplist, node));
if (skiplist.Head.DistanceRightTo(skiplist.Head) > 1)
{
var newHead = skiplist.NodeFactory(skiplist.Head.Key);
newHead.ConnectTo(newHead);
newHead.ConnectDownTo(skiplist.Head);
skiplist.Head = newHead;
}
}
public static Skiplist <T> CreateFrom <T>(IEnumerable <T> keys)
{
var keyList = keys.ToList();
var skiplist = new Skiplist <T>(MinimumGapSize);
if (keyList.Any())
{
var head = CreateOrderedCircularList(keyList, skiplist.NodeFactory);
while (head.LengthOfList() > 1)
{
head = CreateNextLevel(head, skiplist.NodeFactory);
}
skiplist.Head = head;
}
return(skiplist);
}
public static INode <T> FetchNode <T>(
this Skiplist <T> skiplist,
T key,
INode <T> origin = null,
Action <INode <T> > pathAction = null)
{
if (skiplist.Head == null)
{
return(null);
}
var node = origin ?? skiplist.Head;
var atCorrectNode = false;
while (!atCorrectNode)
{
node = FindCorrectGapInLevel(key, node, skiplist.InOrder, skiplist.AreEqual);
if (pathAction != null)
{
pathAction(node);
}
if (node.Down != null)
{
node = node.Down;
}
else
{
atCorrectNode = true;
}
}
return(node);
}
