private NodeMeta Remove(NodeMeta meta)
{
Node node = meta.Node;
Side side = Side.Left;
Node child = node[side];
if (child == null)
{
side = Side.Right;
child = node[side];
}
if (child == null)
{
// adjust color through parent.
if (node.Color == Color.Black)
{
// Black-Black
var sentinel = new SentinelNode();
meta.ParentMeta.Node[meta.SideFromParent] = sentinel;
var sentinelMeta = new NodeMeta(meta.ParentMeta, sentinel, meta.SideFromParent, meta.Sibling);
return(sentinelMeta);
}
else
{
// Red with Black Parent. Done.
meta.ParentMeta.Node[meta.SideFromParent] = null;
return(null);
}
}
else
{
NodeMeta leaf = SwapWithAdjacent(meta, side);
return(Remove(leaf));
}
}
/// <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);
}
}
private NodeMeta SwapWithAdjacent(NodeMeta meta, Side side)
{
Side otherSide = OtherSide(side);
NodeMeta adjacentMeta = Adjacent(side, meta);
Node adjacent = adjacentMeta.Node;
Node toBeReplaced = meta.Node;
Node adjacentParent = adjacentMeta.ParentMeta.Node;
adjacentParent[otherSide] = adjacent[side];
// Swap the nodes.
// Cache the children of item to be replaced.
Node child = adjacent[side];
// Adjacent takes place of node to be removed.
meta.ReplaceNode(adjacent);
meta.ParentMeta.Node[meta.SideFromParent] = adjacent;
adjacent[side] = toBeReplaced[side];
adjacent[otherSide] = toBeReplaced[otherSide];
// Put node to be replaced in adjacent spot
adjacentParent[otherSide] = toBeReplaced;
toBeReplaced[side] = child;
toBeReplaced[otherSide] = null; // This is null, that is how we know it is the leaf
adjacentMeta.ReplaceNode(toBeReplaced);
// Swap the color
Color temp = toBeReplaced.Color;
toBeReplaced.Color = adjacent.Color;
adjacent.Color = temp;
if (child == null)
{
// We have found the node to remove. Replace it with a sentinal
SentinelNode sentinel = new SentinelNode(toBeReplaced.Color);
adjacentParent[otherSide] = sentinel;
return(new NodeMeta(adjacentMeta.ParentMeta, sentinel, adjacentMeta.SideFromParent, adjacentMeta.Sibling));
}
else
{
return(SwapWithAdjacent(adjacentMeta, side));
}
}