private void Rotate(TNode node, RBTreeDirection direction)
{
RBTreeDirection oppositeDirection = OppositeDirection(direction);
//replacement will rotate to where node was, pushing node down
TNode replacement = node.GetChild(oppositeDirection);
node.SetChild(replacement.GetChild(direction), oppositeDirection);
if (replacement.GetChild(direction) != SentinelNode)
{
replacement.GetChild(direction).parent = node;
}
if (replacement != SentinelNode)
{
replacement.parent = node.parent;
}
if (node.HasParent)
{
node.parent.SetChild(replacement, node.ChildDirection);
}
else
{
Root = replacement;
}
replacement.SetChild(node, direction);
if (node != SentinelNode)
{
node.parent = replacement;
}
}
/// <summary>
/// Enumerate the nodes in the tree.
/// </summary>
public IEnumerable <TNode> GetNodes(bool ascending)
{
RBTreeDirection direction = (ascending ? RBTreeDirection.Right : RBTreeDirection.Left);
for (TNode node = SentinelNode.GetNeighbor(direction); node != SentinelNode; node = node.GetNeighbor(direction))
{
yield return(node);
}
}
internal void SetChild(TNode child, RBTreeDirection direction)
{
if (direction == RBTreeDirection.Left)
{
left = child;
}
else
{
right = child;
}
}
private void RestorePropertiesAfterRemove(TNode node)
{
while (node != Root && node.color == RBTreeNodeColor.Black)
{
RBTreeDirection direction = node.ChildDirection;
RBTreeDirection oppositeDirection = OppositeDirection(direction);
TNode sibling = node.Sibling;
if (sibling.color == RBTreeNodeColor.Red)
{
sibling.color = RBTreeNodeColor.Black;
node.parent.color = RBTreeNodeColor.Red;
Rotate(node.parent, direction);
sibling = node.parent.GetChild(oppositeDirection);
}
if ((sibling.left.color == RBTreeNodeColor.Black) &&
(sibling.right.color == RBTreeNodeColor.Black))
{
sibling.color = RBTreeNodeColor.Red;
node = node.parent;
}
else
{
if (sibling.GetChild(oppositeDirection).color == RBTreeNodeColor.Black)
{
sibling.GetChild(direction).color = RBTreeNodeColor.Black;
sibling.color = RBTreeNodeColor.Red;
Rotate(sibling, oppositeDirection);
sibling = node.parent.GetChild(oppositeDirection);
}
sibling.color = node.parent.color;
node.parent.color = RBTreeNodeColor.Black;
sibling.GetChild(oppositeDirection).color = RBTreeNodeColor.Black;
Rotate(node.parent, direction);
node = Root;
}
}
node.color = RBTreeNodeColor.Black;
}
private TNode FindExtremum(Predicate <TKey> predicate, RBTreeDirection direction)
{
RBTreeDirection oppositeDirection = OppositeDirection(direction);
TNode extremum = null;
TNode node = Root;
while (node != SentinelNode)
{
if (predicate(node.Key))
{
extremum = node;
node = node.GetChild(direction);
}
else
{
node = node.GetChild(oppositeDirection);
}
}
return(extremum);
}
private TNode TraverseToFindNeighbor(TNode node, RBTreeDirection direction)
{
if (node.GetChild(direction) == SentinelNode)
{
while (node.HasParent && node.ChildDirection == direction)
{
node = node.parent;
}
return(node.HasParent ? node.parent : SentinelNode);
}
else
{
node = node.GetChild(direction);
RBTreeDirection oppositeDirection = OppositeDirection(direction);
while (node.GetChild(oppositeDirection) != SentinelNode)
{
node = node.GetChild(oppositeDirection);
}
return(node);
}
}
private void RestorePropertiesAfterAdd(TNode node)
{
while (node != Root && node.parent.color == RBTreeNodeColor.Red)
{
TNode uncle = node.parent.Sibling;
if (uncle != null && uncle.color == RBTreeNodeColor.Red)
{
TNode parent = node.parent;
TNode grandparent = parent.parent;
grandparent.color = RBTreeNodeColor.Red;
parent.color = RBTreeNodeColor.Black;
uncle.color = RBTreeNodeColor.Black;
node = grandparent;
}
else
{
RBTreeDirection grandparentToParent = node.parent.ChildDirection;
RBTreeDirection parentToNode = node.ChildDirection;
if (grandparentToParent != parentToNode)
{
node = node.parent;
Rotate(node, grandparentToParent);
}
TNode parent = node.parent;
TNode grandparent = parent.parent;
grandparent.color = RBTreeNodeColor.Red;
parent.color = RBTreeNodeColor.Black;
Rotate(grandparent, OppositeDirection(grandparentToParent));
}
}
Root.color = RBTreeNodeColor.Black;
}
private TNode FindRangeExtremum(KeyRangePredicate rangePredicate, RBTreeDirection direction)
{
TNode extremum = null;
TNode node = Root;
while (node != SentinelNode)
{
int result = rangePredicate(node.Key);
if (result == 0)
{
extremum = node;
node = node.GetChild(direction);
}
else if (result < 0)
{
node = node.right;
}
else
{
node = node.left;
}
}
return(extremum);
}
internal TNode GetChild(RBTreeDirection direction)
{
return(direction == RBTreeDirection.Left ? left : right);
}
internal TNode GetNeighbor(RBTreeDirection direction)
{
return(direction == RBTreeDirection.Left ? predecessor : successor);
}
private static RBTreeDirection OppositeDirection(RBTreeDirection dir)
{
return(dir == RBTreeDirection.Left ? RBTreeDirection.Right : RBTreeDirection.Left);
}