/// <summary>
/// Applies rebalances
/// </summary>
/// <param name="node">Node</param>
/// <param name="selfSize">Size of the subtree the node represents</param>
private void Rebalance(IBinaryTreeNode <TKey, TValue> node, long selfSize)
{
//Find the scapegoat
long currSize = selfSize;
long siblingSize, nodeSize;
IBinaryTreeNode <TKey, TValue> current = node;
do
{
//Get the sibling subtree size
siblingSize = current.GetSibling <TKey, TValue>().GetSize <TKey, TValue>();
if (current.Parent != null)
{
//Total size of the Node is Current size of this subtree plus size of
//sibling subtree plus one for the current node
nodeSize = currSize + siblingSize + 1;
current = current.Parent;
//Is the current node weight balanced?
if (currSize <= (this._balanceFactor * nodeSize) && siblingSize <= (this._balanceFactor * siblingSize))
{
//Weight balanced so continue on
currSize = nodeSize;
}
else
{
//Not weight balanced so this is the scapegoat we rebalance from
break;
}
}
else
{
//Rebalance at the root is gonna be O(n) for sure
break;
}
} while (current != null);
//Check how we need to rebuild after the rebalance
IBinaryTreeNode <TKey, TValue> parent = current.Parent;
bool rebuildLeft = false;
if (parent != null)
{
rebuildLeft = ReferenceEquals(current, parent.LeftChild);
}
//Now do a rebalance of the scapegoat which will be whatever current is set to
IBinaryTreeNode <TKey, TValue>[] nodes = current.Nodes.ToArray();
foreach (IBinaryTreeNode <TKey, TValue> n in nodes)
{
n.Isolate();
}
int median = nodes.Length / 2;
//Console.WriteLine("m = " + median);
IBinaryTreeNode <TKey, TValue> root = nodes[median];
root.LeftChild = this.RebalanceLeftSubtree(nodes, 0, median - 1);
root.RightChild = this.RebalanceRightSubtree(nodes, median + 1, nodes.Length - 1);
//Don't use this check because it's expensive, may be useful to turn of for debugging if you ever have issues with the ScapegoatTree
//if (root.Nodes.Count() != nodes.Length) throw new InvalidOperationException("Scapegoat rebalance lost data, expected " + nodes.Length + " Nodes in rebalanced sub-tree but got " + root.Nodes.Count());
//Use the rebalanced tree in place of the current node
if (parent == null)
{
//Replace entire tree
this.Root = root;
}
else
{
//Replace subtree
if (rebuildLeft)
{
parent.LeftChild = root;
}
else
{
parent.RightChild = root;
}
}
//Reset Max Node code after a rebalance
this._maxNodeCount = this._nodeCount;
}
