/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.util;
import org.apache.commons.math3.exception.MathIllegalArgumentException;
/**
* A strategy to pick a pivoting index of an array for doing partitioning.
* @see MedianOf3PivotingStrategy
* @see RandomPivotingStrategy
* @see CentralPivotingStrategy
* @since 3.4
*/
public interface PivotingStrategyInterface {
/**
* Find pivot index of the array so that partition and K<sup>th</sup>
* element selection can be made
* @param work data array
* @param begin index of the first element of the slice
* @param end index after the last element of the slice
* @return the index of the pivot element chosen between the
* first and the last element of the array slice
* @throws MathIllegalArgumentException when indices exceeds range
*/
int pivotIndex(double[] work, int begin, int end)
throws MathIllegalArgumentException;
}