jdk中提供的快速排序的实现
/* * Copyright (c) 1996, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. *//** * Sort: a class that uses the quicksort algorithm to sort an * array of objects. * * @author Sunita Mani */package sun.misc;public class Sort { private static void swap(Object arr[], int i, int j) { Object tmp; tmp = arr[i]; arr[i] = arr[j]; arr[j] = tmp; } /** * quicksort the array of objects. * * @param arr[] - an array of objects * @param left - the start index - from where to begin sorting * @param right - the last index. * @param comp - an object that implemnts the Compare interface to resolve thecomparison. */ public static void quicksort(Object arr[], int left, int right, Compare comp) { int i, last; if (left >= right) { /* do nothing if array contains fewer than two */ return; /* two elements */ } swap(arr, left, (left+right) / 2); last = left; for (i = left+1; i <= right; i++) { if (comp.doCompare(arr[i], arr[left]) < 0) { swap(arr, ++last, i); } } swap(arr, left, last); quicksort(arr, left, last-1, comp); quicksort(arr, last+1, right, comp); } public static void quicksort(Object arr[], Compare comp) { quicksort(arr, 0, arr.length-1, comp); }}?
pivot使用的中间元素