///<summary>Initialize new instance of <see cref="SkipList{T}"/></summary>
///<param name="keyCompare"><see cref="Comparison{T}"/> callback indication comparison between two <see cref="{T}"/> object</param>
///<param name="pFactor">Parameter specifying probability of level height in new node</param>
///<example>
///pFactor is used as probability factor in randomization of level height in new node.
///Probability: p = 1/pFactor.
///pFactor cannot be smaller or equal to 1, becouse new height will grow to inifinity.
///Count of nodes on level 'L' in list with 'N' added nodes
///probably will be: N*(p^L)
///where p=1/pFactor.
///For bigger pFactor, levels will grow slowly and vice versa.
/// </example>
public SkipList(Comparison <T> keyCompare, double pFactor)
{
this.keyCompare = keyCompare;
this.random = new Random(Environment.TickCount);
this.head = new SLNode <T>(default(T), new SLNode <T> [4]);
this.pFactor = pFactor;
}
///<summary>Checks if list contains key</summary>
///<param name="key">Key to check</param>
///<returns>Returns true if <see cref="SkipList{T}"/> contains key otherwise return false</returns>
public bool Contains(T key)
{
SLNode <T> current = head;
for (int h = head.Level - 1; h >= 0; h--)
{
while (current.NextExist(h))
{
int cResult = keyCompare(key, current.GetNextKey(h));
//Console.Write(key + "-" + current.GetNextKey(h) + ":");
if (cResult == 0)
{
return(true);
}
else if (cResult > 0)
{
current = current.Next[h];
}
else
{
break;
}
}
// Console.WriteLine();
}
return(false);
}
private void ExtendHeadLevel(int newSize)
{
SLNode <T>[] newNodes = new SLNode <T> [newSize];
for (int i = 0; i < head.Level; i++)
{
newNodes[i] = head.Next[i];
}
head = new SLNode <T>(head.Key, newNodes);
}
///<summary>Delete key from list</summary>
public void Delete(T key)
{
//getaddhelpdata can be also used to find where node is
SLNode <T>[] trail = GetAddHelpData(key);
if (trail[0].NextExist(0))
{
if (keyCompare(trail[0].GetNextKey(0), key) == 0)
{
SLNode <T> toDelete = trail[0].Next[0];
for (int i = toDelete.Level - 1; i >= 0; i--)
{
trail[i].SetNext(i, toDelete.Next[i]);
}
}
}
}
///<summary>Insert new key into list</summary>
public void Add(T key)
{
int newNodeLevel = GetRandomLevel();
if (newNodeLevel > head.Level)
{
ExtendHeadLevel(newNodeLevel);
}
SLNode <T>[] update = GetAddHelpData(key);
SLNode <T> newNode = new SLNode <T>(key, new SLNode <T> [newNodeLevel]);
for (int i = newNodeLevel - 1; i >= 0; i--)
{
newNode.SetNext(i, update[i].Next[i]);
update[i].SetNext(i, newNode);
}
}
public void Show()
{
for (int i = 0; i < head.Level; i++)
{
SLNode <T> node = head.Next[i];
while (true)
{
if (node == null)
{
Console.Write("nul");
break;
}
else
{
Console.Write(node.Key.ToString() + "->");
}
node = node.Next[i];
}
Console.WriteLine();
}
}
private SLNode <T>[] GetAddHelpData(T key)
{
SLNode <T>[] update = new SLNode <T> [head.Level];
SLNode <T> current = head;
for (int i = head.Level - 1; i >= 0; i--)
{
while (current.NextExist(i))
{
if (keyCompare(key, current.GetNextKey(i)) > 0)
{
current = current.Next[i];
}
else
{
break;
}
}
update[i] = current;
}
return(update);
}