public static long[] PreComputeHashes(
string Text, int P, long p, long x)
{
int T = Text.Length;
long[] result = new long[T - P + 1];
string S = Text.Substring(T - P, P);
result[T - P] = Q2HashingWithChain.PolyHash(S, 0, S.Length, p, x);
long y = 1;
for (long i = 1; i <= P; i++)
{
y = (y * x) % p;
}
for (int i = T - P - 1; i >= 0; i--)
{
result[i] = (x * result[i + 1] + (p * 10) +
Convert.ToInt32(Text[i]) -
(y * Convert.ToInt32(Text[i + P]))) % p;
}
return(result);
}
public long[] Solve(string pattern, string text)
{
List <long> occurrences = new List <long>();
int P = 1000000007;
Random random = new Random();
long x = random.Next(1, P - 1);
long pHash = Q2HashingWithChain.PolyHash(pattern, 0,
pattern.Length, P, x);
long[] Hashes = PreComputeHashes(text, pattern.Length, P, x);
for (int i = 0; i <= text.Length - pattern.Length; i++)
{
if (pHash != Hashes[i])
{
continue;
}
if (text.Substring(i, pattern.Length) == pattern)
{
occurrences.Add(i);
}
}
return(occurrences.ToArray());
}
