001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.math4.legacy.stat.descriptive.rank;
018
019/**
020 * A strategy to pick a pivoting index of an array for doing partitioning.
021 *
022 * @see MedianOf3PivotingStrategy
023 * @see RandomPivotingStrategy
024 * @see CentralPivotingStrategy
025 * @since 4.0
026 */
027public interface PivotingStrategy {
028    /**
029     * Find pivot index of the array so that partition and K<sup>th</sup>
030     * element selection can be made.
031     * @param work data array
032     * @param begin index of the first element of the slice
033     * @param end index after the last element of the slice
034     * @return the index of the pivot element chosen between the
035     * first and the last element of the array slice
036     * @throws IllegalArgumentException when indices exceeds range
037     */
038    int pivotIndex(double[] work, int begin, int end);
039}