Java 中的快速排序
快速排序算法基于分治法，通过选择一个枢轴元素将数组划分为子数组。
在划分数组时，pivot 元素的定位方式应使小于pivot 的元素保留在左侧，大于pivot 的元素保留在右侧。
对左右子数组继续相同的过程。最后，将排序后的元素组合起来形成一个排序数组。
要了解更多信息，请访问快速排序算法。
示例: 实现快速排序算法的 Java 程序
import java.util.Arrays; class Quicksort { // method to find the partition position static int partition(int array[], int low, int high) { // choose the rightmost element as pivot int pivot = array[high]; // pointer for greater element int i = (low-1); // traverse through all elements // compare each element with pivot for (int j = low; j < high; j++) { if (array[j] <= pivot) { // if element smaller than pivot is found // swap it with the greater element pointed by i i++; // swapping element at i with element at j int temp = array[i]; array[i] = array[j]; array[j] = temp; } } // swapt the pivot element with the greater element specified by i int temp = array[i + 1]; array[i + 1] = array[high]; array[high] = temp; // return the position from where partition is done return (i + 1); } static void quickSort(int array[], int low, int high) { if (low < high) { // find pivot element such that // elements smaller than pivot are on the left // elements greater than pivot are on the right int pi = partition(array, low, high); // recursive call on the left of pivot quickSort(array, low, pi-1); // recursive call on the right of pivot quickSort(array, pi + 1, high); } } } // Main class class Main { public static void main(String args[]) { int[] data = { 8, 7, 2, 1, 0, 9, 6 }; System.out.println("Unsorted Array"); System.out.println(Arrays.toString(data)); int size = data.length; // call quicksort() on array data Quicksort.quickSort(data, 0, size-1); System.out.println("Sorted Array in Ascending Order "); System.out.println(Arrays.toString(data)); } }
输出
Unsorted Array [8, 7, 2, 1, 0, 9, 6] Sorted Array in Ascending Order [0, 1, 2, 6, 7, 8, 9]
这里，数组的元素是按升序排列的。如果我们想按降序对元素进行排序，那么在
for循环中，我们可以将代码改成:
// the less than sign is changed to greater than if (array[j] >= pivot) {
