干货，使用布隆过滤器实现高效缓存！

public class BloomFilter {     //布隆缓存数组     public BitArray BloomCache;     //布隆缓存数组的长度     public Int64 BloomCacheLength { get; }      public Int64 HashCount { get; }           /// <summary>     ///      /// </summary>     /// <param name="bloomCacheLength">布隆缓存数组的长度，默认20000</param>      /// <param name="hashCount">hash运算次数，默认3</param>     public BloomFilter(int bloomCacheLength = 20000,  int hashCount = 3)     {         BloomCache = new BitArray(bloomCacheLength);         BloomCacheLength = bloomCacheLength;          HashCount = hashCount;     }     public void Add(string str)     {         var hashCode =str.GetHashCode();         Random random = new Random(hashCode);         for (int i = 0; i < HashCount; i++)         {             var x = random.Next((int)(BloomCacheLength - 1));             BloomCache[x] = true;         }     } ​     public bool IsExist(string str)     {         var hashCode = str.GetHashCode();         Random random = new Random(hashCode);         for (int i = 0; i < HashCount; i++)         {             if (!BloomCache[random.Next((int)(BloomCacheLength - 1))])             {                 return false;             }         }         return true;     } ​     //错误率查看     public double GetFalsePositiveProbability(double setSize)     {         // (1 - e^(-k * n / m)) ^ k         return Math.Pow((1 - Math.Exp(-HashCount * setSize / BloomCacheLength)), HashCount);     }     //计算基于布隆过滤器散列的最佳数量，即hashCount的最佳值     public int OptimalNumberOfHashes(int setSize)     {         return (int)Math.Ceiling((BloomCacheLength / setSize) * Math.Log(2.0));     } ​ }

 public partial class Form1 : Form     {         BloomFilter bloom = new BloomFilter(20000, 3);         int setSize = 2000;         public Form1()         {             InitializeComponent();             //生成布隆缓存数组             for (int i = 0; i < setSize; i++)             {                 bloom.Add("kiba" + i);             }         }          private void btnSearch_Click(object sender, EventArgs e)         {              Stopwatch sw = new Stopwatch();             sw.Start();             string con = tbCon.Text.Trim();             var ret = bloom.IsExist(con);             sw.Stop();             lblRet.Text = $@"结果:{ret}{Environment.NewLine} 耗时:{sw.ElapsedTicks}{Environment.NewLine} 错误概率:{bloom.GetFalsePositiveProbability(setSize)}{Environment.NewLine}  最佳数量:{bloom.OptimalNumberOfHashes(setSize)}";          }      }