Rabin karp algorithm to study

RabiinKarp.cs

/// <summary>
        /// Rabin Karp string search algorithm.
        /// </summary>
        /// <param name="haystack">The haystack.</param>
        /// <param name="needle">The needle.</param>
        /// <returns>The list of index.</returns>
        public static List<int> RabinKarp(string haystack, string needle)
        {
            var result = new List<int>();
            if (string.IsNullOrWhiteSpace(haystack) || string.IsNullOrWhiteSpace(needle) || (needle.Length > haystack.Length)) return result;

            int m = needle.Length, n = haystack.Length, needleHash = 0, haystackHash = 0, mostSignificantDigitHash = 1; ;
            const int Mod = 101, NumberBase = 256;

            for (int i = 0; i < m - 1; i++)  // The value of h would be "pow(NumberBase, m-1)%q"  
                mostSignificantDigitHash = (mostSignificantDigitHash * NumberBase) % Mod;

            for (int i = 0; i < m; i++)
            {
                needleHash = ((NumberBase * needleHash) + needle[i]) % Mod;
                haystackHash = ((NumberBase * haystackHash) + haystack[i]) % Mod;
            }

            for (int i = 0; i <= n - m; i++)
            {
                if (needleHash == haystackHash)
                {
                    for (int j = 0; j <= m; j++)
                    {
                        if (j == m) result.Add(i);
                        else if (haystack[i + j] != needle[j]) break;
                    }
                }

                if (i < n - m)
                {
                    haystackHash = ((NumberBase * (haystackHash - (haystack[i] * mostSignificantDigitHash))) + haystack[i + m]) % Mod;
                    if (haystackHash < 0) haystackHash = (haystackHash + Mod);
                }
            }

            return result;
        }