集合中随机取不重复的索引

 

 

有时候希望从一个集合中随机取n个元素不重复

那么就取到这n个数字的索引

 public static int[] GetRandomArray(int Number, int minNum, int maxNum)
        {
            int j;
            int[] b = new int[Number];
            Random r = new Random(GetRandomSeed());
            for (j = 0; j < Number; j++)
            {
                int i = r.Next(minNum, maxNum + 1);
                int num = 0;
                for (int k = 0; k < j; k++)
                {
                    if (b[k] == i)
                    {
                        num = num + 1;
                    }
                }
                if (num == 0)
                {
                    b[j] = i;
                }
                else
                {
                    j = j - 1;
                }
            }
            return b;
        }

注意重置随机数的种子 批量操作时候不会取到一样的

//提高随机数不重复概率的种子
        static int GetRandomSeed()
        {
            byte[] bytes = new byte[4];
            System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
            rng.GetBytes(bytes);
            return BitConverter.ToInt32(bytes, 0);
        }

测试：

  for (int i = 0; i < 100; i++)
            {
                string[] result = GetRandomArray(10, 0, 12).Select(t => Convert.ToString(t)).ToArray();
                 Console.WriteLine(string.Join(",", result));
            }
            Console.ReadKey();

结果：

 

public static int[] GetRandomArray(int Number, int minNum, int maxNum)

参数number 取几个索引   minnum 索引的最小值(可取到)  maxNum 索引的最大值(可取到的)