public void GetSiblingFindsNoSiblingWhenNoneExists()
{
PointerBackedBinaryTreeNode <string> testNode = new PointerBackedBinaryTreeNode <string>("abc", null);
testNode.Left = new PointerBackedBinaryTreeNode <string>("def", testNode);
Assert.IsNull(testNode.GetSibling());
Assert.IsNull(testNode.Left.GetSibling());
}
private void DeleteRepair(PointerBackedBinaryTreeNode <RedBlackTreeNode <T> > node)
{
if (node.Parent != null)
{
// If this node isn't the root, we need to...
PointerBackedBinaryTreeNode <RedBlackTreeNode <T> > sibling = node.GetSibling();
if (!sibling.Data.IsBlack)
{
// ... reverse colors
sibling.Parent.Data.IsBlack = false;
sibling.Data.IsBlack = true;
// .... and rotate around
if (node.Parent.Left == node)
{
this.RotateLeft(node.Parent);
}
else
{
this.RotateRight(node.Parent);
}
}
// Once we do that, we need to possibly ...
if (sibling.Data.IsBlack && sibling.Left.Data.IsBlack && sibling.Right.Data.IsBlack)
{
// ... repeat recursivly or color theparent
sibling.Data.IsBlack = false;
if (node.Parent.Data.IsBlack)
{
DeleteRepair(node.Parent);
}
else
{
node.Parent.Data.IsBlack = false;
}
}
else
{
// ... or perform more rotations with coloration swaps
if (sibling.Data.IsBlack)
{
// Force subsequent rotations to 'do the right thing'
if (node.Parent.Left == node && sibling.Right.Data.IsBlack && !sibling.Left.Data.IsBlack)
{
sibling.Data.IsBlack = false;
sibling.Left.Data.IsBlack = true;
this.RotateRight(sibling);
}
else if (node.Parent.Right == node && sibling.Left.Data.IsBlack && !sibling.Right.Data.IsBlack)
{
sibling.Data.IsBlack = false;
sibling.Right.Data.IsBlack = true;
this.RotateLeft(sibling);
}
}
sibling.Data.IsBlack = node.Parent.Data.IsBlack;
node.Parent.Data.IsBlack = true;
if (node.Parent.Left == node)
{
sibling.Right.Data.IsBlack = true;
this.RotateLeft(node.Parent);
}
else
{
sibling.Left.Data.IsBlack = true;
this.RotateRight(node.Parent);
}
}
}
else
{
this.Root = node;
}
}
