徹底暴力-選擇題解

          while (true)
            {
                int.TryParse(Console.ReadLine(), out int N);
                int[] arr = new int[N];
                Random ran = new Random();
                for (int i = 0; i < arr.Length; i++)
                {
                    arr[i] = ran.Next(1, 1000);
                }
                Stopwatch stopwatch = new Stopwatch();
                stopwatch.Start();
                Sort(arr);
                Console.WriteLine($"第{N / 2}大的數爲：" + arr[N / 2 - 1]);
                stopwatch.Stop();
                TimeSpan tp = stopwatch.Elapsed;
                Console.WriteLine($"程序運行：總毫秒:{tp.TotalMilliseconds}");
            }
                
                    //從大到小
        static int[] Sort(int[] arr)
        {
            int temp;
            for (int i = 0; i < arr.Length - 1; i++)
            {
                for (int j = i + 1; j < arr.Length; j++)
                {
                    if (arr[i] < arr[j])
                    {
                        temp = arr[i];
                        arr[i] = arr[j];
                        arr[j] = temp;
                    }
                }
            }
            return arr;
        }

　　用最簡單的數組索引返回k最大值，時間複雜度慘不忍睹。