public static double Solution()
{
var stopwatch = new Stopwatch();
stopwatch.Start();
var subsetCount = (long)Math.Pow(2, ProblemDigits.Count);
PrimeCandidates = new List <long> [subsetCount];
for (int i = 0; i < subsetCount; i++)
{
PrimeCandidates[i] = new List <long>();
}
var primes = UtilityFunctions.Primes(98765432);
foreach (var p in primes)
{
var digitSignature = UtilityFunctions.DigitSignature(p, ProblemDigits);
if (digitSignature > 0)
{
PrimeCandidates[digitSignature].Add(p);
}
}
return(PandigitalPrimeSets(ProblemDigits));
}
internal static long PandigitalPrimeSets(List <long> digits)
{
if (digits.Count == 0)
{
return(1);
}
long count = 0;
digits.Sort();
var maxElement = digits[digits.Count - 1];
var restOfDigits = UtilityFunctions.Complement(new List <long> {
maxElement
}, digits);
var subsets = UtilityFunctions.GenerateSubsets(restOfDigits);
foreach (var subset in subsets)
{
subset.Add(maxElement);
var complement = UtilityFunctions.Complement(subset, digits);
var subsetDigitSignature = UtilityFunctions.DigitSignature(subset, ProblemDigits);
count += PrimeCandidates[subsetDigitSignature].Count * PandigitalPrimeSets(complement);
}
return(count);
}