org.apache.lucene.util.Selector Maven / Gradle / Ivy
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* 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,
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* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.lucene.util;
/** An implementation of a selection algorithm, ie. computing the k-th greatest
* value from a collection. */
public abstract class Selector {
/** Reorder elements so that the element at position {@code k} is the same
* as if all elements were sorted and all other elements are partitioned
* around it: {@code [from, k)} only contains elements that are less than
* or equal to {@code k} and {@code (k, to)} only contains elements that
* are greater than or equal to {@code k}. */
public abstract void select(int from, int to, int k);
void checkArgs(int from, int to, int k) {
if (k < from) {
throw new IllegalArgumentException("k must be >= from");
}
if (k >= to) {
throw new IllegalArgumentException("k must be < to");
}
}
/** Swap values at slots i and j. */
protected abstract void swap(int i, int j);
}