滚动哈希的Rabin-Karp字符串匹配算法

Question

这是Rabin-Karp字符串匹配算法在C#中的一个实现...

static void Main(string[] args)
{
  string A = "String that contains a pattern.";
  string B = "pattern";
  ulong siga = 0;
  ulong sigb = 0;
  ulong Q = 100007;
  ulong D = 256;
for (int i = 0; i < B.Length; i++)
{
    siga = (siga * D + (ulong)A[i]) % Q;
    sigb = (sigb * D + (ulong)B[i]) % Q;
}
if (siga == sigb)
{
    Console.WriteLine(string.Format(">>{0}<<{1}", A.Substring(0, B.Length), A.Substring(B.Length)));
    return;
}
ulong pow = 1;
for (int k = 1; k <= B.Length - 1; k++)
    pow = (pow * D) % Q;

for (int j = 1; j <= A.Length - B.Length; j++)
{
    siga = (siga + Q - pow * (ulong)A[j - 1] %Q) % Q;
    siga = (siga * D + (ulong)A[j + B.Length - 1]) % Q;
    if (siga == sigb)
    {
        if (A.Substring(j, B.Length) == B)
        {
            Console.WriteLine(string.Format("{0}>>{1}<<{2}", A.Substring(0, j), 
                                                             A.Substring(j, B.Length), 
                                                             A.Substring(j +B.Length)));
            return;
        }
    }
}
Console.WriteLine("Not copied!");

}

但是如果我改变第二个字符串的位置而不是显示结果不是复制但它有一个问题

 string A = "String that contains a pattern.";
 string B = "pattern";

这里显示没有复制

 string A = "String that contains a pattern.";
 string B = "Matches contains a pattern ";

我想检查它是否是从第一个字符串复制的，甚至我会在其中添加一些内容或更改位置，但它不应该有区别，所以如何更改它，它只会比较每个单词的哈希值在字符串中比实现它............

Answer 1

改变

string B = "Matches contains a pattern ";

到

string B = "contains a pattern ";

它会起作用的