java算法----排序----（4）快速排序

package log;

public class Test4 {

    /**
     * java算法---快速排序
     * 
     * @param args
     */
    public static void main(String[] args) {
        // 需要排序的数组
        int arr[] = { 49, 20, 36, 51, 18, 94, 61, 31, 50 };
        // 循环输出该数组内容
        System.out.println("排序之前：");
        for (int a : arr) {
            System.out.print(a + "\t");
        }
        System.out.println();

        if (arr.length > 0) {
            sort(arr, 0, arr.length - 1);
        }
        // 循环输出该数组内容
        System.out.println("排序之后：");
        for (int a : arr) {
            System.out.print(a + "\t");
        }
        System.out.println();

    }

    public static int getMiddle(int[] list, int low, int high) {
        int temp = list[low];
        while (low < high) {
            while (low < high && list[high] >= temp) {
                high--;
            }
            list[low] = list[high];
            while (low < high && list[low] <= temp) {
                low++;
            }
            list[high] = list[low];
        }
        list[low] = temp;
        return low;
    }

    public static void sort(int[] list, int low, int high) {
        if (low < high) {
            int middle = getMiddle(list, low, high);
            sort(list, low, middle - 1);
            sort(list, middle + 1, high);
        }
    }

}

下面这事控制台的输出