现有1~100 共一百个自然数,已随机放入一个有98个元素的数组a[98].要求写出一个尽量简单的方案找出没有被放入数组的那2个数,并在屏幕上打印这2个数

 void test7()
        {
            try
            {
                int[] a = new int[98];
                int[] num = new int[100];
                int[] num1 = new int[100];
                int countnum = 0;
                int counta = 0;
                int i;
                for (i = 0; i < num.Length; i++)
                {
                    num[i] = i + 1;
                    num1[i] = i + 1;//方法1用到
                    countnum = num[i] + countnum;
                }
                //随机放入
                Random rand = new Random();
                int temp; 
                for (i = 0; i < a.Length; i++)
                {
                    while (true)
                    {
                        temp = rand.Next(100);
                        if (num[temp] != 0)
                        {
                            num[temp] = 0;
                            a[i] = temp + 1;
                            break;
                        }
                    }
                } 
                foreach (int aa in a)
                {
                    counta = counta + aa;

                    Console.WriteLine(aa+";");
                }

                #region 方法1 推荐，这才是插入完，再查找
                int diff = countnum - counta;
                List<int> list = num.Where(n => num.Contains(diff - n)).ToList<int>();//验证,num中只剩两个没变0的
                List<int> list1 = num1.Where(n => num1.Contains(diff - n) && !a.Contains(n)).ToList<int>();//查找，针对的是没有处理过得原数组
                Console.WriteLine("list.count:"+list.Count);
                Console.WriteLine("list1.count:" + list1.Count);
                foreach (int nn in list)
                {
                    //if (!a.Contains(nn))
                    //{
                    Console.WriteLine("没有被放入数组的数(list)："); 
                        Console.WriteLine(nn);
                        //Console.WriteLine("bingo");
                    //}
                }
                foreach (int nn in list1)
                { 
                    //if (!a.Contains(nn))
                    //{
                    Console.WriteLine("没有被放入数组的数(list1)："); 
                        Console.WriteLine(nn);
                        //Console.WriteLine("bingo1");
                    //}
                }
                #endregion

                #region 方法2 太投机取巧了，其实是在随机插入的过程中把插入的全置为0，剩下的就是没插入的
                for (i = 0; i < a.Length; i++)
                    if (num[a[i] - 1] != 0)
                        num[a[i] - 1] = 0;
                //输出
                for (i = 0; i < a.Length; i++)
                {
                    if (i % 10 == 0 && i > 0)
                        System.Console.WriteLine();
                    System.Console.Write("{0,4}", a[i]);
                }
                System.Console.WriteLine();
                System.Console.Write("没有被放入数组的2个数：");
                for (i = 0; i < num.Length; i++)
                    if (num[i] != 0)
                        System.Console.Write("{0,4}", num[i]);
                System.Console.WriteLine();
                #endregion
            }
            catch (Exception)
            {

                throw;
            }
        }