1 files changed, 43 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/util/PivotingStrategyInterface.java b/src/main/java/org/apache/commons/math3/util/PivotingStrategyInterface.java
new file mode 100644
index 0000000..0e2b175
--- /dev/null
+++ b/src/main/java/org/apache/commons/math3/util/PivotingStrategyInterface.java
@@ -0,0 +1,43 @@
+/*
+ * 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;
+}