QuicksortTask.java

/*
 * Copyright 2024 Hochschule Luzern Informatik.
 *
 * Licensed 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 ch.hslu.exercises.sw11.ex2.quicksort;

import java.util.concurrent.RecursiveAction;

/**
 * Codevorlage zu RecursiveAction für die Sortierung eines int-Arrays.
 */
public final class QuicksortTask extends RecursiveAction {

    private final int threshold;
    private final int[] array;
    private final int min;
    private final int max;

    /**
     * Erzeugt einen Array-Sortier Task.
     *
     * @param array Interger-Array.
     */
    public QuicksortTask(int[] array, final int threshold) {
        this(array, 0, array.length - 1, threshold);
    }

    private QuicksortTask(final int[] array, final int min, final int max, final int threshold) {
        this.array = array;
        this.min = min;
        this.max = max;
        this.threshold = threshold;
    }

    private static void insertionSort(int[] array, int left, int right) {
        for (int i = left + 1; i <= right; i++) {
            final int key = array[i];
            int j = i - 1;
            while (j >= left && array[j] > key) {
                array[j + 1] = array[j];
                j--;
            }
            array[j + 1] = key;
        }
    }

    @Override
    protected void compute() {
        if (max > min) {
            if (max - min < threshold) {
                insertionSort(array, min, max);
            } else {
                final int pivotIndex = QuicksortRecursive.partition(array, min, max);
                invokeAll(new QuicksortTask(array, min, pivotIndex - 1, threshold), new QuicksortTask(array, pivotIndex + 1, max, threshold));
            }
        }
    }

}