1/*
2 * Copyright (C) 2011 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the
10 * License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
11 * express or implied. See the License for the specific language governing permissions and
12 * limitations under the License.
13 */
14
15package com.google.common.collect;
16
17import com.google.common.annotations.GwtCompatible;
18
19import javax.annotation.Nullable;
20
21/**
22 * A local balancing policy for modified nodes in binary search trees.
23 *
24 * @author Louis Wasserman
25 * @param <N> The type of the nodes in the trees that this {@code BstRebalancePolicy} can
26 *        rebalance.
27 */
28@GwtCompatible
29interface BstBalancePolicy<N extends BstNode<?, N>> {
30  /**
31   * Constructs a locally balanced tree around the key and value data in {@code source}, and the
32   * subtrees {@code left} and {@code right}. It is guaranteed that the resulting tree will have
33   * the same inorder traversal order as the subtree {@code left}, then the entry {@code source},
34   * then the subtree {@code right}.
35   */
36  N balance(BstNodeFactory<N> nodeFactory, N source, @Nullable N left, @Nullable N right);
37
38  /**
39   * Constructs a locally balanced tree around the subtrees {@code left} and {@code right}. It is
40   * guaranteed that the resulting tree will have the same inorder traversal order as the subtree
41   * {@code left}, then the subtree {@code right}.
42   */
43  @Nullable
44  N combine(BstNodeFactory<N> nodeFactory, @Nullable N left, @Nullable N right);
45}
46