public ActionResult Problem35(ulong n)
{
var cal = new PrimeCalculator((uint)n / 3);
cal.ExtendToMinimumGT(n);
Func <ulong, bool> isCircular = (i) =>
{
ulong c = i;
uint numDigits = Utils.NumOfDigits(c);
ulong factor = Utils.PowerOfTen(numDigits - 1);
do
{
ulong lower = (c / 10);
ulong higher = (c % 10) * factor; // Move rightmost digit to leftmost position
c = higher + lower;
if (!cal.IsPrimeInRange(c))
{
return(false);
}
}while (c != i);
return(true);
};
int cnt = cal.Primes.Count(isCircular);
return(ViewAnswer(35, "The number of circular primes below " + n + " is", (uint)cnt));
}
