快速排序算法

/**
     * 快速排序
     */
    public static int[] quickSort(int[] array) {
        quick(array);
        return array;
    }

    private static int getMiddle(int[] list, int low, int high) {
        int tmp = list[low];
        while (low < high) {
            while (low < high && list[high] >= tmp) {
                high--;
            }

            list[low] = list[high];
            while (low < high && list[low] <= tmp) {
                low++;
            }

            list[high] = list[low];
        }
        list[low] = tmp;
        return low;
    }

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

    }

    private static void quick(int[] a2) {
        if (a2.length > 0) {
            middleSort(a2, 0, a2.length - 1);
        }
    }

运行

/**
     * 待排序的数组
     */
    private static int[] array = {
            12, 10, 5, 9, 5, 32, 16, 1, 9, 99, 80, 3, 18, 19, 20, 25, 7, 15
    };

    public static void main(String[] args) {

        int[] result = SortUtils.quickSort(array.clone());
        System.out.println(Arrays.toString(result));

    }

输出

[1, 3, 5, 5, 7, 9, 9, 10, 12, 15, 16, 18, 19, 20, 25, 32, 80, 99]