QuickSortSnippet.java

/*
 * MIT License
 *
 * Copyright (c) 2017-2022 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package algorithm;

/**
 * QuickSortSnippet.
 */
public class QuickSortSnippet {

  /**
   * Sort an array with quicksort algorithm.
   *
   * @param arr   array to sort
   * @param left  left index where to begin sort (e.g. 0)
   * @param right right index where to end sort (e.g. array length - 1)
   */
  public static void quickSort(int[] arr, int left, int right) {
    var pivotIndex = left + (right - left) / 2;
    var pivotValue = arr[pivotIndex];
    var i = left;
    var j = right;
    while (i <= j) {
      while (arr[i] < pivotValue) {
        i++;
      }
      while (arr[j] > pivotValue) {
        j--;
      }
      if (i <= j) {
        var tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
        i++;
        j--;
      }
      if (left < i) {
        quickSort(arr, left, j);
      }
      if (right > i) {
        quickSort(arr, i, right);
      }
    }
  }
}