private static int TreeLeaning(IImmutableTree <TKey, TValue> tree)
{
if (tree.IsEmpty)
{
return(0);
}
return(TreeHeight(tree.Right) - TreeHeight(tree.Left));
}
private IImmutableTree <TKey, TValue> RotateRightRight(IImmutableTree <TKey, TValue> tree)
{
if (tree.Left.IsEmpty)
{
return(tree);
}
var rotatedLeftChild = new ImmutableTree <TKey, TValue>(_comparer, _keyCloner, _valueCloner, tree.RootKey,
tree.RootValue, RotateLeft(tree.Left), tree.Right);
return(RotateRight(rotatedLeftChild));
}
private IImmutableTree <TKey, TValue> RotateRight(IImmutableTree <TKey, TValue> tree)
{
if (tree.Left.IsEmpty)
{
return(tree);
}
return(new ImmutableTree <TKey, TValue>(_comparer, _keyCloner, _valueCloner, tree.Left.RootKey, tree.Left.RootValue,
tree.Left.Left,
new ImmutableTree <TKey, TValue>(_comparer, _keyCloner, _valueCloner, tree.RootKey,
tree.RootValue, tree.Left.Right, tree.Right)));
}
internal ImmutableTree(IComparer <TKey> comparer, Func <TKey, TKey> keyCloner, Func <TValue, TValue> valueCloner,
TKey key, TValue value,
IImmutableTree <TKey, TValue> left,
IImmutableTree <TKey, TValue> right)
{
_comparer = comparer;
_keyCloner = keyCloner;
_valueCloner = valueCloner;
_key = key;
_value = value;
_left = left;
_right = right;
_height = 1 + Math.Max(TreeHeight(_left), TreeHeight(_right));
Count = 1 + Left.Count + Right.Count;
}
private IEnumerable <IImmutableTree <TKey, TValue> > Descending()
{
var st = ImmutableStack <IImmutableTree <TKey, TValue> > .Start;
for (IImmutableTree <TKey, TValue> each = this; !each.IsEmpty || !st.IsEmpty; each = each.Left)
{
while (!each.IsEmpty)
{
st = st.Push(each);
each = each.Right;
}
each = st.Peek();
st = st.Pop();
yield return(each);
}
}
private IImmutableTree <TKey, TValue> BalanceTree(IImmutableTree <TKey, TValue> tree)
{
IImmutableTree <TKey, TValue> result;
if (RightHeavy(tree))
{
result = LeansLeft(tree.Right) ? RotateLeftLeft(tree) : RotateLeft(tree);
}
else if (LeansLeft(tree))
{
result = RightHeavy(tree.Left) ? RotateRightRight(tree) : RotateRight(tree);
}
else
{
result = tree;
}
return(result);
}
private static bool LeansLeft(IImmutableTree <TKey, TValue> tree)
{
return(TreeLeaning(tree) <= _negHeavy);
}
private static bool RightHeavy(IImmutableTree <TKey, TValue> tree)
{
return(TreeLeaning(tree) >= _heavy);
}
private static int TreeHeight(IImmutableTree <TKey, TValue> tree)
{
return(tree.IsEmpty ? 0 : ((ImmutableTree <TKey, TValue>)tree)._height);
}
