快速排序的改进方法

参考：三种改进快排方法

我是看到算法书的课后题，要求改进快排，在线性表中的第一个元素、中间元素和最后元素中选择一个中位数作为主元

/**
     * 关键：该算法在数组中选择一个称为主元的元素，将数组分为两部分；
     * 每次划分都将主元放在了恰当的位置
     * 时间复杂度：O(nlogn)
     * @param list
     */

    public static void quickSort(int[] list) {
        quickSort(list, 0, list.length - 1);
    }

    private static void quickSort(int[] list, int first, int last) {
        // TODO Auto-generated method stub
        if (first < last) {
              paritionMedianOfTree(list, first, last);
            int privotIndex = partition(list, first, last);
//          int privotIndex = partition2(list, first, last);System.out.println(privotIndex);
            quickSort(list, first, privotIndex - 1);
            quickSort(list, privotIndex + 1, last);
        }
    }

    /**
     * 分割list,从first到last
     * 
     * @param list
     * @param first
     * @param last
     * @return
     */
    private static int partition(int[] list, int first, int last) {

        int pivot = list[first];
        int low = first + 1;
        int high = last;
        int temp = 0;
        while (high > low) {
            // 从左向右找一个比pivot大的数字
            while (low <=high && list[low] <= pivot)
                low++;
            // 从右到左找一个比pivot小的数字
            while (high >= low && list[high] >pivot)
                high--;
            // 找到以后交换两个数
            if (high > low) {
                 temp = list[low];
                list[low] = list[high];
                list[high] = temp;
            }
        }

        while (high > first && list[high] > pivot)
            high--;
        //如果主元被移动，就返回主元移动后的下标
            if (list[high]return high;
            }else {
                //没有被移动就返回原始下标
                return first;
            }

    }

/**
 * 三个数中确定基准值，将确定好的
 * @param attr
 * @param low
 * @param high
 */
 public  static void paritionMedianOfTree(int[] attr,int low,int high) {
          int mid = low + (high -low +1)/2;
          int cas = 0;
               if (attr[mid]>attr[high]) {
                  cas = attr[mid];
                    attr[mid] = attr[high];
                    attr[high] = cas ;
            }

               if (attr[low]>attr[high]) {
                   cas  = attr[low];
                    attr[low] = attr[high];
                    attr[high] = cas ;
            }
               if (attr[mid] >attr[low]){
                    cas  = attr[mid];
                    attr[mid] = attr[low];
                    attr[low] = cas ; 
            }       

}

效率比原来快