private static int IndexFirstPalindromeOfLength(int l, ArrayHashComputer <T> a, ArrayHashComputer <T> aReversed)
{
Debug.Assert(a.Length == aReversed.Length);
if (l <= 1)
{
return(0);
}
for (int start = 0; start < (a.Length - l + 1); ++start)
{
int end = start + l / 2 - 1;
var aHash = a.Hash(start, end);
int reverStart = a.Length - (start + l);
var aReverseHash = aReversed.Hash(reverStart, reverStart + l / 2 - 1);
if (aHash == aReverseHash)
{
return(start);
}
}
return(-1);
}
/// <summary>
/// finds the index of first sub array of length 'subArrayLength' that can be found both in 'this and 'other' array in o (this.Length) time
/// if 'subArrayLength == 0', it will return 0 (the first occurence of an empty string is at index 0)
/// </summary>
/// <param name="other"></param>
/// <param name="subArrayLength">the exact length of the sub array to find</param>
/// <returns>index of the sub array in the 'this' array, or -1 if no such array of length 'subArrayLength' exists</returns>
public int FirstIndexOfSameSubArrayWithLength(ArrayHashComputer <T> other, int subArrayLength)
{
if (subArrayLength <= 0)
{
return(0);
}
var hashInOtherArray = new HashSet <long>();
for (var startIndex = 0; startIndex <= other.Length - subArrayLength; ++startIndex)
{
hashInOtherArray.Add(other.Hash(startIndex, startIndex + subArrayLength - 1));
}
for (var startIndex = 0; startIndex <= Length - subArrayLength; ++startIndex)
{
if (hashInOtherArray.Contains(Hash(startIndex, startIndex + subArrayLength - 1)))
{
return(startIndex);
}
}
return(-1); //there is no common array of length 'subArrayLength' in 'this' and 'other' array
}
