public void BatchDelete()
{
// The constructed AVL Tree would be
// 30
// / \
// 20 40
// / \ \
// 10 25 50
var tree = new AvlTree <int>();
tree.Insert(10);
tree.Insert(20);
tree.Insert(25);
tree.Insert(30);
tree.Insert(40);
tree.Insert(50);
tree.Insert(60);
tree.Insert(70);
tree.Insert(80);
tree.Insert(90);
tree.Insert(100);
var toRemove = tree.FirstOrderedSubsequence(node => node.Key >= 20 && node.Key < 35);
var removedCount = tree.BatchDelete(toRemove.Select(node => node.Key));
Assert.That(removedCount, Is.EqualTo(3));
tree.TraversalMode = TraversalMode.InOrder;
var actual = tree;
CollectionAssert.AreEqual(new[] { 10, 40, 50, 60, 70, 80, 90, 100 }, actual);
AssertTreeIsBalanced(tree);
}