生成一定范围内的互不相同的随机数的方法比较

实现原理：

方法1：使用list，通过list.contains()作为循环判断的条件，实现无重复的add

方法2：使用两组数组，all存储所有可取值，result存储结果，result依次从all中取值，all长度递减，通过索引实现all中始终保持取完后剩下的元素

分析：法1在最坏情况下会重复循环，法2通过保证每次都能取到值，很大程度上提高了效率

代码比较：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;

namespace 基本语法
{
    class Program
    {
        static void Main(string[] args)
        {
            Stopwatch watch = new Stopwatch();
            watch.Start();
            List<int> list = _GetRandom(20, 500, 400);
            watch.Stop();
            int ctrl = 0;
            foreach (int i in list)
            {
                Console.Write("{0} ", i);
                ++ctrl;
                if (ctrl % 20 == 0)
                    Console.WriteLine();
            }
            Console.WriteLine("\nMethod 1 time used:{0}", watch.Elapsed);

            watch.Reset();
            watch.Start();
            int[] ia = GetRandom(20, 500, 400);
            watch.Stop();
            ctrl = 0;
            foreach (int i in ia)
            {
                Console.Write("{0} ", i);
                ++ctrl;
                if (ctrl % 20 == 0)
                    Console.WriteLine();
            }
            Console.WriteLine("\nMethod 2 time used:{0}", watch.Elapsed);
        }
        /// <summary>
        /// 使用list容器产生一定范围内互不相同的随机数
        /// </summary>
        /// <param name="minVal">最小值</param>
        /// <param name="maxVal">最大值</param>
        /// <param name="amount">随机数总数</param>
        /// <returns>返回list<int></returns>
        static List<int> _GetRandom(int minVal, int maxVal, int amount)
        {
            List<int> list = new List<int>();
            while (list.Count != amount)
            {
                Random random = new Random((int)DateTime.Now.Ticks);
                int temp = random.Next(minVal, maxVal);
                if (!list.Contains(temp))
                    list.Add(temp);
            }
            return list;
        }

        /// <summary>
        /// 使用数组方法实现
        /// </summary>
        /// <param name="minVal"></param>
        /// <param name="maxVal"></param>
        /// <param name="amout"></param>
        /// <returns>返回int[]</returns>
        static int[] GetRandom(int minVal, int maxVal, int amout)
        {
            int[] result = new int[amout];
            int[] all = new int[maxVal-minVal+1];
            for (int ix = 0; ix!=amout;++ix )
            {
                all[ix] = minVal + ix;
            }
            Random random = new Random();
            int allNum = all.Length;
            for (int ix = 0; ix != amout;++ix )
            {
                int index=random.Next(allNum);
                result[ix] = all[index];
                all[index] = all[--allNum];
            }
            return result;
        }
    }
        
}

运行结果：

方法1在很多情况下耗时根本无法接受。。。