1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.math4.legacy.stat.descriptive.rank;
18
19 /**
20 * A strategy to pick a pivoting index of an array for doing partitioning.
21 *
22 * @see MedianOf3PivotingStrategy
23 * @see RandomPivotingStrategy
24 * @see CentralPivotingStrategy
25 * @since 4.0
26 */
27 public interface PivotingStrategy {
28 /**
29 * Find pivot index of the array so that partition and K<sup>th</sup>
30 * element selection can be made.
31 * @param work data array
32 * @param begin index of the first element of the slice
33 * @param end index after the last element of the slice
34 * @return the index of the pivot element chosen between the
35 * first and the last element of the array slice
36 * @throws IllegalArgumentException when indices exceeds range
37 */
38 int pivotIndex(double[] work, int begin, int end);
39 }