public override long Solve()
{
for (int i = 9; i > 0; i--)
{
var pandigitals = Pandigitals.Generate(i).OrderByDescending(p => p);
foreach (var pandigital in pandigitals)
{
if (Primes.IsPrime(pandigital))
{
return(pandigital);
}
}
}
return(0);
}
//12.5 seconds without filtering out invalid pandigitals.
//filtering inputs:
//Filter out pandigitals where d6 is not divisble by 5: 11.4 seconds
public override long Solve()
{
var primes = Primes.CalculatePrimesBelow(18).ToArray();
var pandigitals = Pandigitals.GenerateZeroToN(9);
long sum = 0;
foreach (var pandigital in pandigitals)
{
if (PossibleSubstringDivisibleByPrime(pandigital))
{
var divisibleByPrime = true;
for (int i = 0; i < primes.Length && divisibleByPrime; i++)
{
divisibleByPrime = SubstringDivisibleBy(pandigital, i + 1, primes[i]);
}
if (divisibleByPrime)
{
sum += pandigital;
}
}
}
return(sum);
}