快速排序

        /// <summary>
        /// 快速排序
        /// 原理：将数组分成两组，前面一组比后面一组小，然后前后两组依次再次划分，直到全部有序 [ref List<int> nums]
        /// </summary>
        /// <param name="nums">待排序数组</param>
        /// <param name="left">数组第一个数下标</param>
        /// <param name="right">数组总个数</param>
        public static int[] QuickSort(int[] nums, int left, int right)
        {
            if (left < right)
            {
                int i = left;
                int j = right - 1;
                int middle = nums[(left + right) / 2];  //找到数字中间值
                //[9 8 6 7 5 3 2 4 1 7]
                while (true)
                {
                    while (i < right && nums[i] < middle) { i++; };  //左边的数小于中间的数，下标向右移
                    while (j > 0 && nums[j] > middle) { j--; };      //左边的数大于右边的数，下标向左移
                    if (i == j) break;
                    nums[i] = nums[i] + nums[j];  //nums[i]、nums[j]交换
                    nums[j] = nums[i] - nums[j];
                    nums[i] = nums[i] - nums[j];
                    if (nums[i] == nums[j]) j--;
                }
                QuickSort(nums, left, i);
                QuickSort(nums, i + 1, right);
            }
            return nums;
        }