public void Add(T item)
{
var updates = BuildUpdateTable(item);
var current = updates[0];
if (current[0] != null && _comparer.Compare(current[0].Value, item) == 0)
{
// Duplicate value
return;
}
var newNode = new SkipListNode <T>(item, ChooseRandomHeight(_head.Height + 1));
_count++;
if (newNode.Height > _head.Height)
{
_head.IncrementHeight();
_head[_head.Height - 1] = newNode;
}
for (int i = 0; i < newNode.Height; i++)
{
newNode[i] = updates[i][i];
updates[i][i] = newNode;
}
}
public bool Remove(T value)
{
var updates = BuildUpdateTable(value);
SkipListNode <T> current = updates[0][0];
if (current != null && _comparer.Compare(current.Value, value) == 0)
{
_count--;
for (int i = 0; i < _head.Height; i++)
{
if (updates[i][i] != current)
{
break;
}
else
{
updates[i][i] = current[i];
}
}
if (_head[_head.Height - 1] == null)
{
_head.DecrementHeight();
}
return(true);
}
else
{
return(false);
}
}
public SkipList(int randomSeed, IComparer <T> comparer)
{
_head = new SkipListNode <T>(1);
_count = 0;
if (randomSeed < 0)
{
_randomNumber = new Random();
}
else
{
_randomNumber = new Random(randomSeed);
}
_comparer = comparer == null ? _comparer : comparer;
}
public SkipListNode <T> BuildUpdateTable(T item)
{
var updates = new SkipListNode <T>(_head.Height);
var current = _head;
for (int i = _head.Height - 1; i > 0; i--)
{
while (current[i] != null && _comparer.Compare(current[i].Value, item) < 0)
{
current = current[i];
}
updates[i] = current;
}
return(updates);
}
